The sum of the angles of a triangle is 180°.
The angles you know are 28° and 36°, so you can do this to find ∠B:
∠A + ∠B + ∠C = 180°
or 28° + ∠B + 36° = 180° Add 28 and 36
64° + ∠B = 180° Subtract 64 on both sides
∠B = 116
