a. a=40° (alternate interior angles)
b+40°=180°( supplementary angles)
b=140°
c= d= 140°( vertically opposite angles)
d=b=140°( corresponding angles)
b. 2a+120°=180° (supplementary angles)
2a=60°
a=30°
c. a+110°=180°( supplementary angles)
a=70°
b+70°=180°( supplementary angles)
b=110°
c+110°=180°( supplementary angles)
c=70°
c=d=70( corresponding angles)
