Final answer:
The ratio that represents the number of non-fiction books Rita has read is 3/1.
Step-by-step explanation:
To find the ratio of the number of non-fiction books Rita has read, we can use the information given in the question. The ratio is 9 non-fiction books for every 3 fiction books. Simplifying this ratio, we get 9/3, which is equal to 3/1. So, the ratio that represents the number of non-fiction books Rita has read is 3/1.