Mrs. Billy’s second grade class of thirty students conducted a pet ownership survey. Results of the survey indicate that 8 students own a car, 15 students own a dog, wnd 5 students own both a cat and a dog. how many of the students surveyed own only a dog?

To find the number of students who own only a dog, we need to subtract the number of students who own both a cat and a dog from the total number of students who own a dog.

Since 15 students own a dog and 5 students own both a cat and a dog, the number of students who own only a dog is 15 - 5 = <<15-5=10>>10. Answer: \boxed{10}.

To find out how many of the students surveyed own only a dog, we need to subtract the number of students who own both a cat and a dog from the total number of students who own a dog.

The total number of students who own a dog is 15, and the number of students who own both a cat and a dog is 5.

So, the number of students who own only a dog can be calculated as:

15 - 5 = 10

Therefore, 10 of the students surveyed own only a dog.