One day work of A when he complete the work in n days

A complete (7)/(10) of a work in 15 days.After that he completes the work in 4 days with help from B.Find the number of days to complete the whole work if A and b work together from start.

1 man and 1 woman together can complete a piece of work in 8 days. A man alone can complete the work in 10 days. In how many days, can one woman alone complete the work?

If A & B completed a work together in 6 days . If A completed the same work in 10 days alone . Then in how many days will B complete the same work alone ?