Question

In the parallelogram ABCD If angel A = 100 .Find the measure of angel B and angel C

Answer 1

angle a + angle b = 180 (they form supplementary angles)
100 + angle b = 180
angle b = 180 - 100 = 80°

angle a = angle c = 100°   (opposite angles of a parallelogram are equal)
angle b = angle d = 80°     (opposite angles of a parallelogram are equal)

Answer 2

Given angle A = 100
So, angle C =100     (opposite angles in a  parallelogram are equal )
angle B = 180-100    (Angles on the same side of the transversal are 
              =80               supplementry)