I'm just starting to learn how to use javascript and it is my first language. 
What I'm trying to do is have each radio button subtract an amount from the input amount. Right now it is only works for 1 radio button. If I click 2 it just subtracts from the bottom one.

```html
<!doctype html>

<html lang="en">

<head>
  <meta charset="utf-8">
  <title>Numbers Test</title>
</head>

<body>
  <form name="operation_form">
    <label>Verify</label>
    <br/>
    <label>Acert Score:</label><input type="number" name='acertscore' />
    <br/>
    <input type="radio" name="rad1" id="rad1" value='-100' />100
    <br/>
    <input type="radio" name="rad2" id="rad2" value='-200' />200
    <br/>
    <input type="radio" name="rad3" id="rad3" value='-250' />250
    <br/>
    <input type="button" value="Calculate" onclick="operationForm();" />
    <br/>
    <label>Score total is:</label><input type="text" name="answerbox">
    <br/>
    <input type="button" value="Reset" onClick="this.form.reset()" />
  </form>
  <script type="text/javascript">
    function operationForm() {
      var form = document.forms["operation_form"];

      var x = form["acertscore"].value;

      var operation = null;
      var answer = null;

      if (form["rad1"].checked == true) {
        answer = x - 100;
      }
      if (form["rad2"].checked == true) {
        answer = x - 200;
      }
      if (form["rad3"].checked == true) {
        answer = x - 250;
      }

      form["answerbox"].value = answer;
    }
  </script>
</body>

</html>
```

I'm sure I'm going at this the wrong way. If there is an easier way I would love to learn it.