Answer:
C. 20/12 = 100/x
Explanation:
The ratio of interest is (fruit juice)/(total liquid) = x/100. The usual way that would be expressed is ...
(12 cups)/(12 cups + 8 cups) = x/100
12/20 = x/100
We note that the only answer choice with the numbers 12, 20, and 100 is C. Checking that against the expected relation above, we see that both sides are inverted, so the proportion of C is equivalent to the one we expect.