Ratios can be better understood if you read 24:26 as: Emily read 24 fiction books for every 26 books.
The question tells us Emily read 24 fiction books and 2 nonfiction books. We know she read 24 fiction books so that is the first part of our ratio. Now, they want to know how many total books did she read. Well, she read 24 fiction and 2 nonfiction. 24+2 = 26. 26 books total! So now we have the second part of our ratio and end up with the ratio of 24:26. But now, we have to simplify it. Simplifying ratios is like simplyfing fractions. You have to find their greatest common factor. The greatest common factor of 24 and 26 is 2. Now you divide both number by their greatest common factor (2). Finally, we end up with the ratio of 12:13.
Greatest common factor help: https://www.mathsisfun.com/greatest-common-factor.html
