http://try.jquery.com/levels/4/challenges/15

gistfile1.html

<div class="tour" data-daily-price="357">
  <h2>Paris, France Tour</h2>
  <p>$<span id="total">0</span> for <span id="nights-count">2</span> Nights</p>
  <p>
    <label for="nights">Number of Nights</label>
  </p>
  <p>
    <input id="nights" value="7" type="number">
  </p>
</div>
$(document).ready(function() {
  $("#nights").on("keyup", function() {
    var nights = $(this).val();
    var daily_price = $(this).closest('.tour').data('daily-price');
    var total = daily_price * nights;
    $("#nights-count").text(nights);
    $("#total").text(total);
  });
});