Answer:
a.

b. Yes, p || r.
Explanation:
a.
From the figure,
Since, p || q,
(∵ Alternate exterior angles are equal for parallel lines)
This gives,

Now, q || r
∴
(∵ Corresponding angles are equal for parallel lines)
This gives,

Now, since r is a straight line,
and
are supplementary angles.

Therefore,
.
b.

Since, alternate exterior angles
and
are equal, the lines p and r are parallel because, alternate exterior angles are equal only if two lines are parallel.