Answer:
C. 20
Step-by-step explanation:
The two bottom inside angles are identical.
This means that 5x +13 and 3x+7 need to equal 180 degrees.
5x +13 + 3x +7 = 180
Combine like terms:
8x +20 = 180
Subtract 20 from each side:
8x = 160
Divide both sides by 8:
X = 160 / 8
X = 20
