So ∠ ABC+∠ Abd = 90+50 = 140.

So ∠ CBE =180-(∠ ABC+∠ Abd) =180-(90+50) = 40.

(Definition of right angle)

Because ∠ c = 40.

So ∠ c =∠ CBE = 40.

So AB//CD

(Internal dislocation angles are equal and two straight lines are parallel)

Note: point e is on the right of straight line D.