A, B, and C can do a piece of work individually in 20 days, 24 days, and 30 days respectively. A works for only 'x' days, B works for only 'x + 5' days, and C works for only '2x' days. If they complete the entire work together in this manner, then find the value of 'x'.

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?