x = 13, assuming they are the same length.
Using the pythagorean Theorem formula (a^2 + b^2 + c^2) Plug in A and B (13, and 13).
(13)^2 + (13)^2 = c^2
13 • 13 + 13 • 13 = c^2
169 + 169 = c^2
v/338 = v/c^2 (square root them both)
Then you can have your answer for y, hope this helps