Tolong!! yg no 3 bagian (a) aja

Sifat trapesium sama kaki : sudut yang berdekatan sama besar
maka b = 40°
5a = c

c + 5a = 360° – 40° – b
c + c = 360° – 40° – 40°
2c = 280°
c = 140°
5a = 140°
a = 140° : 5 = 28°
jadi a = 28° b = 40° dan c = 140°
semoga membantu ya