Aiden needs 15 liters of cleaning solution. he can buy a 2-gallon jug ($4.28) a 3 gallon jug ($5.92) a 4 gallon jug ($6.56) a 7 gallon jug ($12.98). which jug should he purchase to get at least 15 liters of cleaning solution and spend the least amount of money?

We need 15 liters
2 gallon jug  4.28*2=8.56   1 gallon=3.78, 2 gallons=7.57 liters

3 gallon jug  5.92*3=17.76                        3 gallons=11.35 liters

4 gallon jug  6.56*4=26.24                        4 gallons=15.14 liters

the best solution is to buy 2 times the 2 gallon jug because he will spent
8.56*2=17.12  for 4 gallons(aprox 15 liters)
instead of the 4 gallon jug which costs 26.24

7 gallon this is more expensive and he does not that much solution