The C.P of 15 books is equal to the S.P of 18 books. Find his gain% or loss%?

A. 16 2/3% loss
B. 100/3% loss
C. 50/3% profit
D. 100/3% loss
Explanation:
15 CP = 18 SP
18 — 3 CP loss
100 — ? => 16 2/3% loss