Answer:
written below for problem #2
Explanation:
a. ratio is 12:40 since they're are 12 non fiction and 40 graphic novels
b. 40:12 (same reasoning as part a)
c. 6:40 for the ratio of science fiction to graphic novel, 12:6 for the ration of non fiction to science fiction, x:6 for the ratio of the unknown amount of fiction books to the science fiction books. (x is just there as a variable so it just represents fiction books)