Your answer is very close to being correct; however, the true answer is actually

without any parenthesis needed around the fraction. Notice how there is no (x) at the end.
There are 16 cups in 1 gallon:
16 x 2.75 = 44 cups
More information is needed to answer you.
The answer is actually D. The limit on the left side is computing the derivative at x = a. The right side value of 7 tells us that f ' (a) = 7