There are two difficulties in answering this. The first is that I'm not sure what the question means. Was there any more information in the context?
Possibly it is assuming that any pairing of an initial station and a destination station counts as a different "journey" (but it's the same "journey" and "ticket" if taken at a different time or by a different person!), so you are being asked to count the number of different ordered pairs (x, y), where x and y are any two stations. If there are N stations, how would you calculate the number of such "journeys"? Then you could solve an equation that says this expression is equal to 552. This will give a reasonable answer, so I guess it's what the problem means.
The second difficulty is that you've said nothing about what work you have done, or what you have learned, so I can't be sure what kind of help will be appropriate. If what I've said isn't enough, please show what you have tried, and also tell us what sort of topics the test covers (say, about how to count things like this).