Как перемножить отдельные radioButtons?

Попробуйте так:

from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(742, 600)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        
        self.radioButton = QtWidgets.QRadioButton(self.centralwidget)
        self.radioButton.setGeometry(QtCore.QRect(90, 160, 82, 17))
        self.radioButton.setObjectName("radioButton")
        self.buttonGroup = QtWidgets.QButtonGroup(MainWindow)
        self.buttonGroup.setObjectName("buttonGroup")
        self.buttonGroup.addButton(self.radioButton)
        self.radioButton_2 = QtWidgets.QRadioButton(self.centralwidget)
        self.radioButton_2.setGeometry(QtCore.QRect(190, 160, 82, 17))
        self.radioButton_2.setObjectName("radioButton_2")
        self.buttonGroup.addButton(self.radioButton_2)
        self.radioButton_3 = QtWidgets.QRadioButton(self.centralwidget)
        self.radioButton_3.setGeometry(QtCore.QRect(280, 160, 82, 17))
        self.radioButton_3.setObjectName("radioButton_3")
        self.buttonGroup.addButton(self.radioButton_3)
        
        self.pushButton = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton.setGeometry(QtCore.QRect(320, 370, 75, 23))
        self.pushButton.setObjectName("pushButton")
        
        self.radioButton_4 = QtWidgets.QRadioButton(self.centralwidget)
        self.radioButton_4.setGeometry(QtCore.QRect(90, 190, 82, 17))
        self.radioButton_4.setObjectName("radioButton_4")
        self.buttonGroup_2 = QtWidgets.QButtonGroup(MainWindow)
        self.buttonGroup_2.setObjectName("buttonGroup_2")
        self.buttonGroup_2.addButton(self.radioButton_4)
        self.radioButton_5 = QtWidgets.QRadioButton(self.centralwidget)
        self.radioButton_5.setGeometry(QtCore.QRect(190, 190, 82, 17))
        self.radioButton_5.setObjectName("radioButton_5")
        self.buttonGroup_2.addButton(self.radioButton_5)
        self.radioButton_6 = QtWidgets.QRadioButton(self.centralwidget)
        self.radioButton_6.setGeometry(QtCore.QRect(280, 190, 82, 17))
        self.radioButton_6.setObjectName("radioButton_6")
        self.buttonGroup_2.addButton(self.radioButton_6)
        
        self.textBrowser = QtWidgets.QTextBrowser(self.centralwidget)
        self.textBrowser.setGeometry(QtCore.QRect(270, 315, 81, 25))
        self.textBrowser.setObjectName("textBrowser")
        self.label = QtWidgets.QLabel(self.centralwidget)
        self.label.setGeometry(QtCore.QRect(30, 130, 151, 16))
        self.label.setObjectName("label")
        
        self.radioButton_7 = QtWidgets.QRadioButton(self.centralwidget)
        self.radioButton_7.setGeometry(QtCore.QRect(430, 160, 82, 17))
        self.radioButton_7.setObjectName("radioButton_7")
        self.buttonGroup_3 = QtWidgets.QButtonGroup(MainWindow)
        self.buttonGroup_3.setObjectName("buttonGroup_3")
        self.buttonGroup_3.addButton(self.radioButton_7)
        self.radioButton_8 = QtWidgets.QRadioButton(self.centralwidget)
        self.radioButton_8.setGeometry(QtCore.QRect(530, 190, 82, 17))
        self.radioButton_8.setObjectName("radioButton_8")
        self.buttonGroup_4 = QtWidgets.QButtonGroup(MainWindow)
        self.buttonGroup_4.setObjectName("buttonGroup_4")
        self.buttonGroup_4.addButton(self.radioButton_8)
        self.radioButton_9 = QtWidgets.QRadioButton(self.centralwidget)
        self.radioButton_9.setGeometry(QtCore.QRect(530, 160, 82, 17))
        self.radioButton_9.setObjectName("radioButton_9")
        self.buttonGroup_3.addButton(self.radioButton_9)
        self.radioButton_10 = QtWidgets.QRadioButton(self.centralwidget)
        self.radioButton_10.setGeometry(QtCore.QRect(620, 190, 82, 17))
        self.radioButton_10.setObjectName("radioButton_10")
        self.buttonGroup_4.addButton(self.radioButton_10)
        self.radioButton_11 = QtWidgets.QRadioButton(self.centralwidget)
        self.radioButton_11.setGeometry(QtCore.QRect(620, 160, 82, 17))
        self.radioButton_11.setObjectName("radioButton_11")
        self.buttonGroup_3.addButton(self.radioButton_11)
        self.radioButton_12 = QtWidgets.QRadioButton(self.centralwidget)
        self.radioButton_12.setGeometry(QtCore.QRect(430, 190, 82, 17))
        self.radioButton_12.setObjectName("radioButton_12")
        self.buttonGroup_4.addButton(self.radioButton_12)
        self.label_2 = QtWidgets.QLabel(self.centralwidget)
        self.label_2.setGeometry(QtCore.QRect(410, 110, 151, 16))
        self.label_2.setObjectName("label_2")
        
        self.textBrowser_2 = QtWidgets.QTextBrowser(self.centralwidget)
        self.textBrowser_2.setGeometry(QtCore.QRect(390, 315, 81, 25))
        self.textBrowser_2.setObjectName("textBrowser_2")
        self.label_3 = QtWidgets.QLabel(self.centralwidget)
        self.label_3.setGeometry(QtCore.QRect(220, 320, 47, 13))
        self.label_3.setObjectName("label_3")
        self.label_4 = QtWidgets.QLabel(self.centralwidget)
        self.label_4.setGeometry(QtCore.QRect(360, 320, 47, 13))
        self.label_4.setObjectName("label_4")
        self.label_5 = QtWidgets.QLabel(self.centralwidget)
        self.label_5.setGeometry(QtCore.QRect(480, 320, 47, 13))
        self.label_5.setObjectName("label_5")
        
        self.textBrowser_3 = QtWidgets.QTextBrowser(self.centralwidget)
        self.textBrowser_3.setGeometry(QtCore.QRect(500, 305, 141, 41))
        self.textBrowser_3.setStyleSheet('font-size: 25px;')
        self.textBrowser_3.setObjectName("textBrowser_3")
        
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 742, 21))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.radioButton.setText(_translate("MainWindow", "1"))
        self.radioButton_2.setText(_translate("MainWindow", "2"))
        self.radioButton_3.setText(_translate("MainWindow", "3"))
        self.pushButton.setText(_translate("MainWindow", "Результат"))
        self.radioButton_4.setText(_translate("MainWindow", "4"))
        self.radioButton_5.setText(_translate("MainWindow", "5"))
        self.radioButton_6.setText(_translate("MainWindow", "6"))
        self.label.setText(_translate("MainWindow", "Коэффициент 1"))
        self.radioButton_7.setText(_translate("MainWindow", "1"))
        self.radioButton_8.setText(_translate("MainWindow", "5"))
        self.radioButton_9.setText(_translate("MainWindow", "2"))
        self.radioButton_10.setText(_translate("MainWindow", "6"))
        self.radioButton_11.setText(_translate("MainWindow", "3"))
        self.radioButton_12.setText(_translate("MainWindow", "4"))
        self.label_2.setText(_translate("MainWindow", "Коэффициент 2"))
        self.label_3.setText(_translate("MainWindow", "20 +"))
        self.label_4.setText(_translate("MainWindow", "+"))
        self.label_5.setText(_translate("MainWindow", "="))


class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self):
        super().__init__()
        self.setupUi(self)

        bg_1 = self.buttonGroup.buttons()
        bg_2 = self.buttonGroup_2.buttons()
        bg_3 = self.buttonGroup_3.buttons()
        bg_4 = self.buttonGroup_4.buttons()
        self.list_bg = (bg_1, bg_2, bg_3, bg_4)

        self.pushButton.clicked.connect(self.func_result)

    def func_result(self):
        _dict_active_rb = []
        for i, rbs in enumerate(self.list_bg):
            fl = False
            for rb in rbs:
                if rb.isChecked():
                    fl = True
                    _dict_active_rb.append(rb.text())
                    continue
            if not fl:
                msg = QtWidgets.QMessageBox.information(
                    self, 'Внимание', 
                    'Выберите все необходимые rb для расчетов.')
                return
                
        print(f'{_dict_active_rb}') 
        rez_1 = int(_dict_active_rb[0]) * int(_dict_active_rb[1])
        self.textBrowser.setPlainText(f'{rez_1}')
        
        rez_2 = int(_dict_active_rb[2]) * int(_dict_active_rb[3])
        self.textBrowser_2.setPlainText(f'{rez_2}')
        self.textBrowser_3.setPlainText(f'{20 + rez_1 + rez_2}')
        

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec())