40% hate roller coasters
60% love roller coasters
out of the 60% that love roller coaster; 20% own chinchilla and 8 students that do not own chinchilla = 100 - 20 = 80

Let the total number of students = 100
40% hate roller coasters => 40% of 100 = 40
i.e 40 hate roller coasters

Total students that love roller coaster = 100 - 40 = 60
Out of the 60 students that love roller coasters; 20% own chinchilla
i.e 20% of 60 students own chinchilla
$$\frac{20}{100}\cdot60=12\ students\ own\ chinchilla$$

Students who does not own chinchilla
=100 - 20 = 80% of 60
$$\frac{80}{100}\cdot60=48\%$$
Answer = option C