9514 1404 393
Answer:
51
Step-by-step explanation:
The exterior angle is equal to the sum of the remote interior angles.
71° = 20° + x°
51 = x . . . . . . . . . divide by °, subtract 20
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Additional comment
Consider the missing interior angle of the triangle. It is 180° - 71°. It is also 180° -20° -x°. Equating these values and rearranging, we get ...
71° = 20° + x°
In short, supplements of the same angle are congruent. This relationship can save you the unnecessary work of figuring out the missing interior angle.
