I'm afraid your equation is not correctly set up. You need to identify the longest side of this right triangle; it is x. This is the "hypotenuse." Next, identify the lengths of the legs: they are sqrt(13) and 2sqrt(2).
Here's a refresher on the Pythagorean Theorem:
(hypotenuse)^2 = (leg 1)^2 + (leg 2)^2
Applying this Theorem here, [x]^2 = [2sqrt(2)]^2 + [sqrt(13)\^2
Solve this for x^2, and then take the positive root (only) of your result.