If Priya and Renu can do a job in 12 hours working together at their respective constant speeds, and Priya can do the job alone in 18 hours, in how many hours can Renu do the job alone?

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?