There is 20x more nonfiction than fiction so you do 20+1=21 so then to find out what of 1155 is we do 1155÷21=55 so then we times 55 by 20 because there are 20x more nonfiction than fiction 55x20=1100 soo now we know there is 1100 nonfiction books and 55 fiction books to check whether we are right we can do 1100=55=1155 we are right because there is 1155 books in the library hope i helped