Answer:
Gallons of punch used = 4.94 gallons
Explanation:
Given that:
Liters of punch purchased = 25 liters 
Liters of punch left over = 6 liters 
Liters of punch used = 25 - 6 = 19 liters 
According to the given statement;
1 liter = 0.26 gallons 
19 liters = 0.26*19 gallons 
19 liters = 4.94 gallons 
Hence, 
Gallons of punch used = 4.94 gallons