Answer:
m∠B = 31°
Step-by-step explanation:
First, find the measure of angle ACB by subtracting its supplement from 180 degrees:
180 - 113 = 77
m∠ACB = 77°
Then subtract both m∠A and m∠ACB from 180 degrees, since the interior angles of a triangle always add to 180°:
m∠B = 180° - 72° - 77°
m∠B = 31°
