what was the rate in gallons per hour that the water was draining

Question

To get ready for summer, a pool was being drained for cleaning. At 9am there was 160 gallons of water in the pool, at 12pm there was 97 gallons of water still left to be drained. What was the rate in gallons per hour that the water was draining? 

Answer 1

From the problem, we have amounts at 9am - 160 gallons, and 12pm - 97 gallons. We're looking for gallons per hour, so on the top of the fraction is the difference in water amounts over the difference in time

(160-97)gallons / 3 hours.

Now you just need to subtract what's in parentheses and then reduce your fraction to know how many gallons are drained in 1 hour.