C and M together can complete 5 times a certain piece of work in 54 days. If C alone can complete the original work in 27 days, in how many days can M alone complete the same original work?

If P and Q together can complete a piece of work in 15 days and P alone can do it in 45 days, in how many days can Q alone complete that work?

A can lay a railway track between two stations in 16 days and B can do the same job in 12 days. With the help of C, they finished the job in 4 days. In how many days can C alone do the job?