Final answer:
To prove that ∠4 is supplementary to ∠15, we can use the transitive property of parallel lines. Corresponding angles formed by parallel lines are congruent. Therefore, ∠4 is supplementary to ∠15.
Step-by-step explanation:
To prove that ∠4 is supplementary to ∠15, we can use the transitive property of parallel lines. Since ∠4 is parallel to ∠15 in both p∥q and r∥s, we can say that ∠4 and ∠15 are corresponding angles. Corresponding angles formed by parallel lines are congruent.
Therefore, ∠4 = ∠15.
Since corresponding angles ∠4 and ∠15 are congruent, they are both supplementary to the same angle. So, ∠4 is supplementary to ∠15.