Answer:
See below.
Step-by-step explanation:
We know that and we want to prove that .
Statements Reasons
1) Given
2) A) Vertical Angles Are Congruent
3) B) Substitution Property
4) C) Alternate Interior Angles Converse*
*We know that alternate interior angles are congruent when two parallel lines are cut by a transversal. So, the converse states that if the two alternate interior angles are congruent, the the two lines must be parallel.
Further Notes:
I'm not sure why they did more than necessary. Since , they are corresponding angles. Then by the Corresponding Angles Converse, p must be parallel to r.