Need help to solve algebra 1 homework

One reservoir will be filled in 12 hours, if two pipes function simultaneously.One pipe fills the reservoir faster than the other pipe. How many hours does it take for the second pipe to fill the reservoir?

Thanks

If two pipes can fill it in 12 hours, then if only one was operating it would take twice as long, or 24 hours, assuming both fill at the same rate. But since one fills faster than the other, the slow one all by itself must take longer than that.

Thank you for you reply...