Answer: 12
Step-by-step explanation: Since the angles are supplements, 3x + x - 20 = 180. Solving this, we find that x = 50, and 3x = 150. Since dodecagons have interior angles of 150 degrees, the answer is 12 sides.
Answer:
21
Step-by-step explanation:
Answer:
Y = - 9
Step-by-step explanation:
Y=-20+x
Y = -20 + 11
Y = - 9
Answer: 22
Step-by-step explanation: