Two input text sum

$(‘#ctrl-generaltestprice,#ctrl-generaltax_vat_per,#ctrl-generaltax_vat_amt’).on(‘input’, function(){
var $sum =0;
var $generaltestprice = $(this).closest(‘form’).find(‘#ctrl-generaltestprice’).val();
var $generaltax_vat_per = $(this).closest(‘form’).find(‘#ctrl-generaltax_vat_per’).val();
var $generaltax_vat_amt_dom = $(this).closest(‘form’).find(‘#ctrl-generaltax_vat_amt’);
var $generaltesttotalamt_dom = $(this).closest(‘form’).find(‘#ctrl-generaltesttotalamt’);
$generaltax_vat_amt = ($generaltestprice * $generaltax_vat_per)/100 ;
$generaltax_vat_amt_dom.val($generaltax_vat_amt);
$generaltesttotalamt = ($generaltestprice + $generaltax_vat_amt);
$generaltesttotalamt_dom.val($generaltesttotalamt);

});

all function working but when this $generaltesttotalamt = ($generaltestprice + $generaltax_vat_amt); not working like addition(+)