A and B together can do a piece of work in 6 days and A alone can do it in 14 days. In how many days can B alone can do it?
Choose one.
A) 12 days B) 15 days C) 21 / 2 days D) 21 days E) 22 days

Rationale: "explanation : a and b can do work 1 / 6 in 1 day a alone can do 1 / 14 work in 1 day b alone can do ( 1 / 6 - 1 / 14 ) = 2 / 21 work in 1 day = > complete work can be done in 21 / 2 days by b answer : option c"
Answer: C