<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<input id="numb1">
+
<input id="numb2">
<button id="sum">=</button>
<input id="numb3">
<script src="/static/jquery/jquery-3.3.1.min.js"></script>
<script type="text/javascript">
$(function(){
$('#sum').click(function (){
$("#numb3").val(Number($('#numb1').val())+Number($('#numb2').val()))
})
})
</script>
</body>
</html>