Answer:
Foot-in-the-door technique
Step-by-step explanation:
Foot-in-the-door technique (FITD) is a tactic which aim is that a person agrees to a large request by make them agree to a smaller request at first.
In this case, you want your parents to finance your planned trip to Europe, asking this would be a very big request. So instead, you try to make them agree to get you a bus ticket to a local city only (smaller request), and this way you expect that later they will be willing to send you on the entire trip to Europe and finance it.
Thus, this is an example of Foot-in-the-door technique.