A and B complete a job in 6 days. A alone can do the job in 9 days. If B works alone, how many days will it take to complete the job?	Select:
A) 12
B) 15
C) 18
D) 21
E) 24
The rate of A and B is 1/6   A's rate is 1/9   B's rate is 1/6 - 1/9 = 1/18   B can complete the job in 18 days.   The answer is 18.
<result>C</result>
A and B complete a job in 6 days. A alone can do the job in 9 days. If B works alone, how many days will it take to complete the job?