To solve this problem, convertion of units should be applied.
First convert 2 quarts to cups
2 quart (4 cups/ quart) = 8 cups
So the total cups is 9 cups
Then convert cups to ounce
9 cups ( 8 ounce/ 1 cuo) = 72 ounce
Since he will bake 10 cupcakes
So the amount of batter left
72 ounce – 10 cupcakes( 6 ounces/ cupacake) = 12 ounces left