Geometry Practice Test 5

Join Line BC.

∠ACB = 90° {angle in a semicircle)
In ΔABC,
∠ACB+∠CAB+∠ABC = 180°
∠ABC = 180° − (20° + 90°)
∠ABC = 70°
∠ABC+∠ADC = 180° (sum of opposite angles of a parallelogram) ∵ AB || CD)
70° +∠ADC = 180°
∠ADC = 180° − 70°
∠ADC = 110°