The numbers in the diagram are correct because they satisfy all the conditions given in the text.
Then, we can easily identify that 9 people ordered quesadillas and chili con queso but not ordered nachos.
On the other hand, 22 people ordered just nachos.
To find the probability that a person chosen at random ordered chili con queso, divide the total amount of people that ordered chili con queso over the total number of people in the sample.
Since 40 people ordered chili con queso and there are 104 people seated in the restaurant, then the probability that a person chosen at random ordered chili con queso is: