Tryit Editor v1.8

Source Code:
<!DOCTYPE html> <html> <head> <script src="../../ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"> </script> <script> $(document).ready(function(){ $("button").click(function(){ $("div").width(function(n,c){ return c-200; }); }); }); </script> </head> <body> <button>Decrease width of div with 200 px.</button> <br><br> <div style="height:100px;border:4px solid;"></div> </body> </html>
Result:
W3Schools.com - Try it yourself