как вычитать '.$row["kg"].'-'.$row["tara"].'

как вычитать '.$row["kg"].'-'.$row["tara"].'

<?php
    //fetch.php
    include('database_connection.php');
    
    $query = "SELECT * FROM sample_data ORDER BY id ASC";
    
        $statement = $connect->prepare($query); 
        $statement->execute();
        $result = $statement->fetchAll();
        $total_row = $statement->rowCount();
        $output = '';
    
        if($total_row > 0)
    {
        foreach($result as $row)
        {
            
            $output .= 
            
            '
            <tr>        
            
            <td>'.$row["id"].'</td>
            <td>'.$row["country"].'</td>
            <td>'.$row["kg"].'</td>
            <td>'.$row["tara"].'</td>
        
        
            
            </tr> 
            '
            ;
        }
    }
    else
    {
        $output .= '
        <tr>
            <td colspan="3" align="center">Пусто</td>
        </tr>
        ';
    }
    
    echo $output;
    
    ?>