Answer:
3 should be put in the box in the upper left corner, since it represents the number of students who have neither a cat or a dog.
15 should be put in the box to the left, since that's how many students who have cats.
Same goes for the box to the right, in which 16 should be put, since 16 students have a dog.
And finally, how do we find the number in the middle?
Well, we know that in 25 students, 3 don't have either a cat or dog, so 22 have pets.
However, the total of the people who have dogs and the people who have cats is 15 + 16 = 31 students!
This is because some people have both cats and dogs.
It's pretty simple to find that number, since all you have to do is to subtract 22 from 31, which comes out to 9.
Hence, 9 should be put in the middle box, which represents students who have both a cat and a dog.
Finally, the probability of a student having both a cat and a dog can be found by 9/25 * 100% = 36%.
Explanation:
Hope this helped!