Answer:
3.84 gallons per person
Explanation:
Simply divide "juice" by "people," because you want to end up with units of "juice per person."
1.92 billion gallons is 1,920,000,000. Was that part throwing you? If so, now it's easy:
1,920,000,000 gallons ÷ 500,000,000 people = 3.84 gallons per person