Answer:
Answer C can not be used to find the new size of the gym.
Explanation:
Let's use process of elimination!
A is stating 1.20x, or 120% of x. This is correct, because we have x and then were increasing by 20%, which is just 120%. A is however not the answer because we are asking which expression below could not be used, and A could be used. B is also incorrect because of what I just stated, x + 0.20x is the same thing as 1.20x. C is 20% of x, but that won't get us the answer. C is the correct answer since it cannot be used to find the new size of the gym, but if you really want to you can check answer D as well. In answer D you can distribute the x to the 1 and the 0.20, and you get x + 0.20x, which is the same as answer B. Therefore C is the correct answer.