Answer:
x = 12; m<ABC = 76
Step-by-step explanation:
The two angles whose measures are given form a linear pair. Therefore, they are supplementary angles, and their measures add up to 180 degrees.
8x - 20 + 116 - x = 180
7x + 96 = 180
7x = 84
x = 12
The angle with measure 8x - 20 and angle ABC are vertical angles. That means that their measures are equal.
m<ABC = 8x - 20 = 8(12) - 20 = 96 - 20 = 76
Answer: x = 12; m<ABC = 76
