Solve the Problem $6 \%$ Cement Should He Mix with 5 Bags Of

Multiple Choice

Solve the problem.
-A contractor mixes concrete from bags of pre-mix for small jobs. How many bags with $6 \%$ cement should he mix with 5 bags of $18 \%$ cement to produce a mix containing $12 \%$ cement?

A) 10 bags
B) 5 bags
C) 15 bags
D) 7 bags