Answer:
∠EFH
Explanation:
If AB and CD are parallel lines and EF is a transversal line, then angles formed on the same side of the transversal line and are exterior to the parallel lines are same side exterior angles.
Same side exterior angles theorem states that same-side exterior angles are supplementary.
From the image attached below:
∠ABC and ∠EFH are same side exterior angles, therefore:
∠ABC + ∠EFH = 180°