The Purplemath Forums

Hi all, I am stumped on how to solve these three problems. I already have the answers (given on sheet), but cannot for the life of me figure out how to get them. Any help would be greatly appreciated.

Solve at+b=ct for t

Solve t(1/a + 1/b) = 1 for t

Solve 5(1/a + 1/b)= 1 for a

Thank you very much. The trick about factoring was what really helped.