Alternate Exterior Angles theorem and Linear Pair theorem.
Explanation:
Alternate exterior angles are ones that are outside the "block" formed by the parallel lines and on opposite sides of the transversal. Both ∠2 and ∠7 are outside the parallel lines; additionally, ∠2 is on the right side of the transversal and ∠7 is on the left. This makes them alternate exterior angles.
A linear pair is a pair of angles that form a straight line. ∠7 and ∠8, when combined, form a straight line; this makes them a linear pair.
