Answer:
Assuming you're referring to the sides of a right triangle, the missing side X would be 12.
Explanation:
The Pythagorean Theorem states that the two legs of a right triangle squared and added together is equal to the hypotenuse squared.
is 169,
is 25, 169 - 25 = 144. Take the square root of 144 and you'll get 12, which is the missing side of the right triangle.