Okay, here are the steps to solve this problem:
* The ponde family's powerjet pump pumps 420 gallons of water per hour.
* That means it pumps 420 / 60 = 7 gallons per minute.
* In 45 minutes there are 45 / 60 = 3/4 of an hour.
* So in 45 minutes the pump will pump 3/4 * 7 = 5.25 gallons of water.
Rounded to the nearest whole number, in 45 minutes the pump will pump 5 gallons of water.