(1) There are six people in each car, and there are two cars. There are actually 12 seats available. There are 3 people in each car and 6 people without cars. The difference between the two sitting methods is 12+6 = 18 seats.

That is to say, a car with 6 people takes more seats than a car with 3 people 18 people. And each car takes 6-3 = 3 people. So there are cars: 18 ÷ 3 = (6 cars).

Someone: 6× (6-2) = 6× 4 = 24 (person)