Isha can do a certain piece of work in 24 days. Isha and Smriti together can do the same work in 20 days, and Isha, Smriti, and Ashlesha can do the same work together in 12 days. In how many days can Isha and Ashlesha together do the same 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?