Only (12-5)=7 pepole are there in the train.
If a dozen people get on a train, and five of them get off at the next stop, how many of those people are left on the train?*
Dozen = 12 People.
Thus, there would be 12 people on the train. So, if 5 people get off the train (or left the train), it will mean 12-5 = 7 people.
Thus, there would be 7 people remaining on the train.