I don't remember how to do these ^^'
(a) Use AAA simularity because the last angles are the same to prove they are similar.
(b) Use similar triangles to get QP/AB=PR/AC, so 4/3 is 28/(3x+6), and through cross-multiplying, 4(3x+6) is 84, and x=5.
HOPE THIS HELPED!
