8 have both that means that of the 11 people that have cats 3 have only cats and of the 13 that have dogs 5 only have dogs therefore 2 people don't have four-legged animals at home
it starts out with 18 students, 24 pets in total. -16 for the dogs and cats, to lead up to 8, and 10 students left after subtracting 8 for how many students don't have a pet at home. So 2 students shouldn't have four legged pets left after subtracting the rest. (this is my answer, it's probably wrong, i think you should wait for more,)
