Find the cost of 4 quarts:
$ 6.99 [Cost of 1 quart] x 4 [Number of quarts] = $27.96 [Cost of 4 quarts]
Find the difference in price between 1 gallon and 4 quarts.
$ 27.96 [Cost of 4 quarts] - 20.99 [Cost of 1 gallon] = $ 6.97 [Difference]
One gallon of paint is less expensive than 4 quarts. The amount you save, $6.97, is just about the price of 1 quart of paint. When you buy the gallon, you get nearly 1 quart free.
Find out how many gallons to buy. Divide the total number of quarts needed by 4. This answer will tell Michael the number of gallons and quarts he needs.
10 ÷4 = 2 Gallons, 2 quarts
Two gallons and 2 quarts are equal to 10 quarts.
Find the cost.
$ 20.99 [Cost per gallon] x 2 = $41.98 [Cost of 2 gallons]
$ 6.99 [Cost per quart] x 2 = $13.98 [Cost of 2 quarts]
$ 41.98 [Cost of 2 gallons] + 1 3.98 [Cost of 2 quarts] = $ 55.96 [Total cost]
10 individual quarts cost $69.90 vs $55.96
So answer is C/2 gallons 2 quarts