Answer:
x = 9
Explanation:
Triangles are similar due to AAA (all angles are congruent due to shared angle and corresponding angles). Thus, the sides are proportional, and we can set up a proportion with corresponding sides:
9/(72 + 9) = (3x - 20)/(3x - 20 + 56)
9/81 = (3x - 20)/(3x + 36)
(1/9) * (3x + 36) = 3x - 20
(3x + 36)/9 = 3x - 20
3x + 36 = (3x - 20)*9
3x + 36 = 27x - 180
36 + 180 = 27x - 3x
216 = 24x
x = 9