A tank initially contains 50 gallons of brine, with 30 pounds of salt in solution. Water runs into the tank at 6 gallons per minute and the well-stirred solution runs out at 5 gallons per minute. How long will it be until there are 25 pounds of salt in the tank?
The amount of time until 25 pounds of salt remain in the tank is minutes.
Hint: This problem is a bit complicated. Set up a differential equation and separate variables.