Answer:
The last answer would be your answer. hope this helps
first polygon
ext. angle=180°-120°
=60°

n=360°/60°
n=6
second polygon
n=2(6)=12
ext. ang= 360°/n = 360°/12° = 30°
int. ang = 180°-30°= 150°
answer is C
D because divide both sides by nine
2x + 2y = 6 . . . . . (1)
x + 3y = -1 . . . . . (2)
(1) x 3 => 6x + 6y = 18 . . . . . (3)
(2) x 2 => 2x + 6y = -2 . . . . . (4)
(3) - (4) => 4x = 20
x = 20/4 = 5