Question

please solve this question

Answer 1

I hope you got your answer.....
any doubt about it then ask in comments box

Answer 2

angle abe +angle bef=180. (co in. angles)
120 + bef =180
bef=180-120=60. eq(1)

similarly angle dce+ceg =180. (. co.in.angle)
ceg+100=180
ceg =180-100
ceg=80. eq(2)

angle bef + angle ceg + bec =180 (angles on a straight line)
bec =180- (80+60). (. from eq 1 &2)
bec=180-140
bec=40