Answer:
x = 8
Explanation:
Since this is a rectangle, we know that each corner's angle is 90 degrees. (The box thing at the bottom right shows this.)
Since the two angles that make up angle E sum up to 90, we can make an equation:
(9x - 6) + (2x + 8) = 90
11x + 2 = 90
11x = 88
x = 8