PQ // BC
then
Angle P = Angle B, A is common angle the two triangles are similar
AP/AB = AQ/AC
8/18 = 12/ AC
AC = 12 * 18/8 = 27 (your ans: D)
AQ + QC = AC
QC = AC - AQ = 27 - 12 = 15 (if it was required)
tan60 = y/8
y = s tan60 = 8sqrt(3) (B)
Next time, post each question separately.
