Tank 1 initially contains 30 gallons of water and 25 ounces of salt, while tank 2 initially contains 20 gallons of water and 15 ounces of salt. water containing 1 ounce/gallon of salt ows (from outside) into tank 1 at a rate 1.5 gallons/minute. the mixture ows from tank 1 to tank 2 at a rate of 3 gallons/minute. water containing 3 ounces/gallon of salt ows into tank 2 at a rate of 1 gallon/minute (from outside). the mixture drains from tank 2 at a rate of 4 gallons/minute, of which some ows back to tank 1 at a rate of 1.5 gallon/minute, while the remainder leaves the system.