Answer:
x = 55
Explanation:
A triangle equals 180 degrees, b will be used to find the missing angle.
21 + 34 + b = 180
55 + b = 180
subtract 55 from both sides
b = 125
A straight line is 180 degrees and the b, the missing angle, and x are supplementary angles so
125 + x = 180
x = 55