Answer:
Here is what I can do with info given
Step-by-step explanation:
1.56 billion gallons div by 500 million people is 3.12 gallons per person.
So you get 3.12 gallons per person
I don't know how many people are in you're class so
you need to take 3.12 times x
x is people in your class
Then you get your final awnser