a 12000-gallon pool is being filled at a rate of 40 gallons per minute. at this rate, how many minutes will it take to fill this pool 3/4 full?

First figure out what 3/4 of the pool is. 

12000* 3/4 
=9000 gallons 

If the rate is 40 gallons per minute, 
9000/40 
=225 minutes 

It would take 225 minutes to fill up 3/4 of the pool.

Hope I helped :)