1$('#isAgeSelected').click(function() {
2 $("#txtAge").toggle(this.checked);
3});
4<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js">
5 </script>
6<input type="checkbox" id="isAgeSelected"/>
7<div id="txtAge" style="display:none">Age is something</div>