title: How to add on checked and subract on unchecked using jquery
body: <p>How can you add 25 when you check that box and subtract 25 when you uncheck it on the number that is inside the span id="preciototal" ?</p>
  
  <p>Take a look here please.
  Its part of a checkout form and the idea is it calculates the total price:</p>
  
  <p><a href="http://jsfiddle.net/9YGBu/2/" rel="nofollow">http://jsfiddle.net/9YGBu/2/</a></p>