Algebra test question?

During the filming of "Master and Commander" the crew used a huge tank filled with enough water to float the HMS Surprise. The crew used two different pipes to fill the tank. If the second pipe was used alone then it would take 10 hours longer than if the first pipe alone was used. If the pipes are used together the job of filling the tank takes 12 hours. How long would the slower pipe take to fill the tank alone?