$(function(){
        $("#submit").click(function(){      
            alert($('input:radio:checked').val());
        });
     });

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table>
       <tr>
         <td>Sales Promotion</td>
         <td><input type="radio" name="q12_3" value="1">1</td>
         <td><input type="radio" name="q12_3" value="2">2</td>
         <td><input type="radio" name="q12_3" value="3">3</td>
         <td><input type="radio" name="q12_3" value="4">4</td>
         <td><input type="radio" name="q12_3" value="5">5</td>
      </tr>
    </table>
<button id="submit">submit</button>