1. You need to find the number of passengers on each departure date;
2. For it you have to join two tables: departure and passenger;
3. Use the name_passenger column from the passenger table and the departure_date column from departure;
4. Join these two tables by the number_of_departure column;
5. Make grouping using the GROUP BY clause by the departure_date column from the departure table.

Here's a short example of the passenger table:

Here's a short example of the departure table: