In ΔABC, DE ∥ BC (Fig. 6.39). Find the values of x, y and z.
x = 30°, y = 40°, z = 110°
By parallel lines, ∠D = ∠B = 30°, ∠E = ∠C = 40°. Then ∠A = 180° − (30°+40°) = 110°.