Answer:
See below
Explanation:
a and 120 form a straight line so they add to 180
a + 120 = 180
Subtract 120 from each side
a = 180-120
a = 60
The sum of the angles of a triangle add to 180
b+ a + 60 =180
b + 60 + 60 = 180
b+120 = 180
Subtract 120 from each side
b = 180-120
b = 60