The question:

In a right angled triangle the second to longest side is 5cm longer than the shortest and the hypotenuse is 3 times longer than the shortest side. Find the exaact length of the hypotenuse.

The answer is (15+30 root2)/7

But I got this 5+root50 through the following working:

Could you please tell me where I went wrong?

http://i83.photobucket.com/albums/j283/ta_lia/ahhh.jpg