Two empty seats are tied together, three passengers A B C and an empty seat A5 5.

But if you want to subtract three vacancies, connect them together, and bind and unbind three vacancies in A B C to form A2 2 at a time, then the total * * * is A 4 4 * A2 2 = 48.

That is, A5 5-A4 4*A2 2= 120-48=72.

If you don't understand, divide the situation in another way.

When two consecutive vacancies are on the leftmost or rightmost side, the other vacancy cannot be adjacent to it. Please select a vacant seat first, and then arrange all passengers, that is, 2*C3 1*A3 3=36.

Then, when two seats are in 2 3 seats or 4 5 seats, first choose another empty seat, and then arrange all passengers to get on the bus, that is, 2 * C21* A3 3 = 24.

The last one is when there are three or four positions in C2 1*A3 3= 12.

All add up to 72, which is the same as the previous method.

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