Question

prove that ab II cd.

Answer 1

angle1 = 55
angle BMN = angle2 + angle3
                   = 20 + 35
                   = 55
therefore angle1 = angle BMN
we can say that AB II MN       (alternate interior angles)
angle3 + angle4 = 35 + 145
                           = 180
we can say that MN II CD       (cointerior angles are supplementary)
now AB II MN II CD
therefore AB II CD