JSFiddle - React, Tailwind, and code Playground

HTML

<form method="post" action="">
<select name="select" id="select" name="select"><option value="1">1</option>
 <option value="2">2</option>
 <option value="3">3</option>
 <option value="4">4</option>
 <option value="5">5</option>
    
    </select>
    
    <br><hr>
 <div id="radioButtons">
 <input type="radio" class="multi" name="radio" id="radio" ivalue="1" data-tvalue="275" value="1185">Earlybird 1 Day Registration  $275<br>
<input type="radio" class="multi" name="radio" id="radio" ivalue="2" data-tvalue="475" value="1186">Earlybird 2 Day Registration  $475<br>

</div>
<br><label id="Total"></label><br></form>

JavaScript

$("input[type=radio],select").change(function() {
  
    var radio = parseFloat($('input[type=radio]:checked').attr("data-tvalue")); 
    var select = parseFloat($('#select').val());
    
    $('#Total').text((select * radio)); 
    
 });