Answer
36 quarts
Work Step by Step
Use a unit fraction with quarts (the unit for your answer) in the numerator, and gallon (the unit being changed) in the denominator. Because 1 gallon = 4 quarts , the necessary unit fraction is
(4 quarts)/(1 gal)
Multiply 9 gal times the unit fraction
9 gal * (4 quarts)/(1 gal) = 36 quarts