Question

如图，AB∥CD，BC∥DE，若∠B=60°则∠D= °

Answer 1

∵AB∥CD
又∵∠B=60°
∴∠C=60°
∵BC∥DE
∴∠D=180°-60°=120°

Answer 2

　　∵AB∥CD∴ ∠B =∠C又∵ ∠B =60°∴∠C=60° 又∵BC∥DE∴四边形BCDE是平行四边形∴∠C+∠D=180°∴∠D=180°-60°=120°