A and B together can do a piece of work in 6 days and A alone can do it in 9 days. In how many days can B alone can do it?  Select the correct option:
A) 12 days
B) 15 days
C) 18 days
D) 21 days
E) 22 days
Explanation:   A and B can do work 1/6 in 1 day   A alone can do 1/9 work in 1 day   B alone can do (1/6 -1/9) =1/18 work in 1 day   =&gt; complete work can be done in 18 days by B   Answer: Option 18 days
<result>C</result>
A and B together can do a piece of work in 6 days and A alone can do it in 9 days. In how many days can B alone can do it?