A Kingda Ka train has 4 seats per car, but the last car has only 2 seats. How many seats are on one Kingda Ka train?

Not enough info here to enable us to find a numerical answer. We don't know how many cars make up the train.

Suppose that c cars make up the train.

Then the number of seats on this train is 4 (c-1) + 2.

Example: if there are a total of 3 cars, the # of seats is 4 (2) + 2, or 10:

4 seats in the first car, 4 seats in the second car, and 2 seats in the third car.