We have to prove p || q, given r || s and that <1 and <4 are supplementary.
We can start with <4 and <7, that form a linear pair. Then, as <4 and <7 are complementary, then <1 and <7 are congruent.
Then, for <1, formed at the intersection of p and r, to be congruent with <7, formed at the intersection of q and s, then, as r || s, p and q have to be parallel.
We can write as statement - reason pair as:
1) Statement: r || s. Reason: Given.
2) Statement: <1 and <4 are supplementary. Reason: Given.
3) Statement: <4 and <7 are supplementary. Reason: Linear pair.
4) Statement: <1 ≅ <7. Reason: Supplements of the same angle are congruent.
5) Statement: p || q. Reason: As r || s, <1 and <7 are corresponding angles. Then p || q.