Answer:
590.76 hours
Step-by-step explanation:
A water tank holds 24,000 gallons
Two-Third of water quantity = 
=
Rate of using water is 650 gallons per day
650 gallons of Water used in day = 1
650 gallons of Water used in hours= 24
1 gallon of Water used in hours= 
16000 gallon of Water used in hours= 
Hence It will take 590.76 hours for 2/3 of the water to be used