Will you help me on num 11

Answer:
Option C, x = 35
Step-by-step explanation:
If two angels are supplementary, they add up to 180
Step 1: Make an equation
3x + 15 + 60 = 180
Step 2: Solve for x
3x + 15 + 60 = 180
3x + 75 - 75 = 180 - 75
3x / 3 = 105 / 3
x = 35
Answer: Option C, x = 35