I have no idea where even to start with this one, so anything will help!
A tank initially contains 60 gal of pure water. Brine containing 1 lb of salt per gallon enters the tank and 2 gal/min and the (perfectly mixed) solution leaves the tank at 3 gal/min; thus tthe tank is empty after exactly one hour. (a) Find the amount of salt in the tank after t minutes. (b) What is the maximum amount of salt ever in the tank?