Help with this ill give brainlest

Which statement justifies why angle ebc measures 90?

Solve each quadratic equation by factoring and using the zero product property. x^2 + 18x = 9x

When solving this problem: 3025/5.5 = a/90.75 you get 49912.5 which would be the length of one of the sides of a square when the area is only 90.75 inches. is that answer correct, why, and how is it possible?