Final answer:
Alternate exterior angles formed when a transversal cuts two parallel lines are congruent, meaning they have equal measures.
Step-by-step explanation:
When two parallel lines are cut by a transversal, the alternate exterior angles are congruent. Alternate exterior angles are the pairs of angles that lie on opposite sides of the transversal and outside the two lines. According to the properties of parallel lines cut by a transversal, these pairs of alternate exterior angles are equal in measure, which means they are congruent.