Untitled

<html>

<head>
    <title></title>
</head>

<body>
        First: <input type='text' id='num1'>
        Second: <input type='text' id='num2'>
        <br>
        <input type="button" onClick="addBy()" value="Add"><br>
        <div id="output"></div>
        <script>
       var output = document.getElementById('output');
       var num1 = document.getElementById('num1');
       var num1 = document.getElementById('num2')
       ;

       function addBy(){
         var a = Number(num1.value);
         var b = "+"
         var c =  Number(num2.value);
         var d = a+c;
          outHTML(a,b,c,d)
       }

       function outHTML(a,b,c,d){
           output.innerHTML += a + ' ' + b + ' ' + c + ' = ' + d + '<br>'
        ;
       }
        </script>
    </body>

</html>