Answer:
I believe the answer is 37
Explanation:
you use the pythagorean theorem first with the smaller square, 5^2 + y^2 = 13^2. that answer gets you 12, then plug 12 in with the 35, so it would be 12^2+ 35^2 = X^2, which I believe would be 37. so sorry of that is not the answer but