A can work three times as fast as B. Together they can finish a job in 18 days. In how many days can A complete the job alone?
Select.
A) 20  B) 24  C) 28  D) 32  E) 36
B's rate is x and A's rate is 3x.   x + 3x = 1/18   x = 1/72   A's rate is 3x = 1/24   A can complete the job in 24 days.   The answer is 24.
<result>B</result>
A can work three times as fast as B. Together they can finish a job in 18 days. In how many days can A complete the job alone?