JSFiddle - React, Tailwind, and code Playground

HTML

<form name="myForm" action="" onsubmit="return validateForm()" method="post">


<label>Your Name</label> <br /><br /><input name="name" type="text" />

<br /><br />
<label>Your Salary</label><br /><br />
<select name="salary">
  <option value="10000">10000</option>
  <option value="20000">20000</option>
  <option value="30000">30000</option>
</select>

<br /><br />
<label>Required Amount</label><br /><br />
<input name="requiredamount" type="radio" value="5000" /> 5000
<input name="requiredamount" type="radio" value="10000" /> 10000
<input name="requiredamount" type="radio" value="15000" /> 15000
<input name="requiredamount" type="radio" value="20000" /> 20000

<br /><br />

<input name="" type="button" value="Get Quote" onclick="addNos()" />


</form>

JavaScript

function validateForm()
{
var x=document.forms["myForm"]["name"].value;
if (x==null || x=="")
  {
  alert("What Is Your Name?");
  return false;
  }
}

function getCheckedRadioId(name) {
    var elements = document.getElementsByName(name);

    for (var i=0, len=elements.length; i<len; ++i)
        if (elements[i].checked) return elements[i].value;
}
function addNos(){
    var a, b, res;
    a= parseFloat(document.myForm.salary[document.myForm.salary.selectedIndex].value);
    alert(a);
    b= parseFloat(getCheckedRadioId("requiredamount"));
    res = a+b;
    window.alert("Hello " + a + " " + b );
}