At first two different pipes running together will fill a tank in minutes. the rate that
water runs through each of the pipes is then adjusted. if one pipe, running alone, takes
1 minute less to fill the tank at its new rate, and the other pipe, running alone, takes
2 minutes more to fill the tank at its new rate, then the two running together will fill the
tank in 7 minutes. find in what time the tank will be filled by each pipe running alone
at the new rates.