Alternate Exterior Angles are pairs of angles found on the exterior of parallel lines but on the opposite side of the transversal.
In the figure below, parallel lines \(m\) and \(n\) are cut by the transversal \(t\).
The pairs of the alternate exterior angles are as follows:
\(\angle{1}\) and \(\angle{3}\)
\(\angle{2}\) and \(\angle{4}\)
Since the transversal intersected parallel lines, the alternate exterior angles are congruent.