Mohan takes 9 hours to mow a large lawn. He and Sohan together can mow it in 4 hours. How long will Sohan take to mow the lawn if he works alone?

A alone can complete a work in 12 days. A and B together can complete it in 8 days. How long will B alone take to complete the work?

Quantity I: A and B together can do a pices of work in 4 days. If A alone can do the same work in 6 days, then B alone can do the same work in? Quantity II: A can do a pices of work in 4 hours, B and C together can do it in 3 hours, while A and C together can do it in 2 hours. How long will B alone take to do it ?

Ravi can do a piece of work in 15 hours while Raman can do it in 12 hours. How long will both take to do it, woking together?