Answer:
a=42°
b=138°
Explanation:
the sum of angles on a triangle is 180°
so
18+120+a=180
138+a=180
a=180-138
a=42
a+b=180 because a ans b are linear pair of angles.
Definiton:A linear pair of angles is formed when two lines intersect. Two angles are said to be linear if they are adjacent angles formed by two intersecting lines. The measure of a straight angle is 180 degrees, so a linear pair of angles must add up to 180 degrees.
a=42 from before
it means that b=180-42=138