ANSWER:
For the trip proposed by Trevon, in attendance would be 10 students and 2 chaperons. That makes a total of 12 individuals. Trevon's calculation of 2.4 cars is faulty because you cannot have a car as a fraction. A car must be a whole number. This means Trevon cannot use 2.4 cars.
A better solution would be to assign up to 4 persons per car, which means Trevor should arrange for 3 cars to convey all 12 persons.
Therefore, Trevor's answer does not make sense.