Examine the diagram. A triangle. Angle B is the exterior angle to angle A. The other 2 exterior angles are 100 degrees and 127 degrees. Follow these steps to apply what you have learned about the angles of a triangle. Find m∠B : 100° + 127° + m∠B = 360° Then, find the measure of angle A. Which is the measure of angle A? 133° 53° 47° 80°