Answer:
(a) m<3 = 103 degrees
(b) m<4 = 77 degrees.
Explanation:
A: The sum of the measures of all three interior angles in a triangle always is 180 degrees. Knowing this, we add the two known interior angles, 20 and 57, then subtract that from 180 to get 103 degrees.
B: The measure of an exterior angle is the sum of the two opposite interior angles. So, we add 57 and 20 to get the m<4 = 77 degrees.