Answer:
25 h
Step-by-step explanation:
If the pumps work simultaneously you can add the rates, considering the third pump with a negative rate because it is draining the pool.
The rate is calculated as V/t
Where V is the volume filled or drained in a given time
First pump rate = 1/3 * 2550 / 2.5 = 340 gallons / h
5 hours and 6 minutes = 5 + 6/60 = 5.1 h
Second pump rate = 1/5 * 2550 / 5.1 = 100 gallons / h
Third pump rate = -338 gallons / h
Total rate = 340 + 100 - 338 = 102 gallons /h
Time needed to fill the pump = 2550 / 102 = 25 h
