Two angles are complementary. one of the angles is twice the other.
the larger angle has a measure of
a) 120°
b) 60°
c) 45°

Two complementary angles must add to 90 degrees, and if you divide 90 into thirds (two parts for the larger angle, one for the smaller), then you get 30 degrees.

If the smaller angle is 30 degrees, then the larger is two times that, which is 60. 60 + 30 = 90, so the larger angle is equal to 60 degrees.

12+3b -1=-5-b -12-1+5=-b-3b -8=-4b