A and B together complete a work in 15 days. A alone can do it in 20 days. In how many days B alone can do it?
A and B together can complete a job in 10 days time. B and C can do the same work in 7 days. C and A can do the same work in 9 days. If A, B and C work individually, in how many days will each take to complete the job?