Answer:
x = 4
Step-by-step explanation:
If A is parallel to B, therefore,
9x + 4 = 5x + 20 (alternate interior angles are congruent)
9x + 4 - 5x = 5x + 20 - 5x (subtraction property of equality)
4x + 4 = 20
4x + 4 - 4 = 20 - 4 (subtraction property of equality)
4x = 16
4x/4 = 16/4 (division property of equality)
x = 4
