#### Answer

$y=10\sqrt{2}$

#### Work Step by Step

Because of the marking on the triangle, we see that x is equal to 10.
The Pythagorean Theorem states that for any right triangle, $a^{2} + b^{2} =c^{2},$ where c is the length of the hypotenuse and a and b are the length of the other two sides. Plugging in the dimensions of the given triangle into the Pythagorean Theorem, we obtain:
$$10^2 + 10^2 =y^{2} \\\\ 200=y^{2} \\\\ y=\sqrt{200} \\ y=10\sqrt{2}$$