Let’s take this step by step. Suppose Box 1 is true, then the car WOULD be in Box 1. That would mean Box 2 and 3 would have to be false.
If Box 1 does indeed have a car that means Box 2 would have to be false and that Box 2 DOES have a car, which means both boxes would have a car and that’s not possible.
So we rule out Box 1. Let’s move onto Box 3. But if the car were in Box 3 that would make the statements for Box 2 and 3 both true, which is against the rules of the riddle.
So it has to be in Box 2 then. Since Box 3 is the one true statement, that means Box 1 actually doesn’t have a car and the car is in Box 2 because it’s false and Box 3 stays as the only true one.