Educational worksheet on organizational behavior problems for students.

Let’s go step by step to solve this problem.

We are told:

- There are 30 students in the class.
- Each student has either a dog, a cat, or both.
- 18 students have a dog.
- 15 students have a cat.
- We need to find how many students have both a dog and a cat.

This is a classic “overlap” problem — some students are counted in both groups (dog owners and cat owners), so if we just add 18 + 15, we’ll be double-counting those who have both.

Let’s think of it like this:

Total students = (students with only dogs) + (students with only cats) + (students with both)

But we don’t know any of those yet. Instead, we can use this idea:

If we add the number of dog owners and cat owners:
18 (dogs) + 15 (cats) = 33

But there are only 30 students total. That means 3 extra counts — which must come from students who were counted twice because they have both a dog and a cat.

So, the number of students who have both = 33 - 30 = 3

✔ Let’s check:

- Students with both: 3
- So, students with only dogs: 18 - 3 = 15
- Students with only cats: 15 - 3 = 12
- Total: 15 (only dogs) + 12 (only cats) + 3 (both) = 30 → matches!

Final Answer:
3