Answer:
The answer is only 6 have dogs
Explanation:
B + C + D - B∩C - B∩D - C∩D + B∩C∩D + x = 35
8 + 12 + 15 - 2 - 4 - 5 + 0 + x = 35
With Dogs only: 15 - (5+4) = 6
Just in case, we can calculate the others too:
With Cats only: 12 - (5+2) = 5
With Birds only: 8 - (4+2) = 2
With dogs and cats: 5
With birds and dogs: 4
With cats and birds: 2
With dogs, cats, and birds : 0
Total students surveyed: 35
6 + 5 + 2 + 5 + 4 + 2 = 24 students with pets
35 - 24 = 11 students have no pets