A record store sells CDs for $12 each. A music club offers 5 free CDs and charges $15 for each additional CD. Which equation can you use to find the number of CDs (x) that will cost the same under both plans?
A. 12x-5=15x
B. 15x-5=12x
C. 12(x-5)=15x
D. 12x=15(x-5)