Question

Find the missing angle measure in ΔQRS.

Q = ____°, R = 60°, S = 20°
A. 80
B. 100
C. 120
D. 60

Answer 1

A triangle always has 180 degrees.
180 = x + 60 + 20
180 = x + 80
100 = x
So our answer is B.

Answer 2

The answer would be B because all 3 angles on a triangle must add up to 180 degrees. Since the two angles you do know add up to 80, you need the last angle to be 100 degrees.