Question

James, Kim, and Katrina each bought lemonade at different stores. James paid $6 per gallon, Kim paid $8 per gallon, and Katrina paid $11 per gallon. Between the three of them, 25 gallons were purchased. If Kim bought 4 more gallons than Katrina and they pooled their lemonade together to sell for $8 per gallon, find the number of gallons James, Kim and Katrina each purchased and explain how you arrived at this answer.