Answer:
65 people
Explanation:
Imagine the situation backwards
Let's say the people who were originally on the train are all wearing red. You end with 63 people. Of these 63 people, 17 of them JUST got on and are wearing blue. So 63 people - 17 blue people is 46 red people (remember, we are trying to find all the RED people). Before all of this happened, 19 people had gotten OFF the train, and these people were part of the original group so they were also red. So now add the 46 red people on the train to the 19 red people that got off and you get 65