Your instructions is to make a database with a number of tables, this you have done, however, the tables are not linked which means it is not a relational database.

There is data entered into the tables, but on investigation I would say all indexing have been manually inputted into the tblRentals. You have to make a normalised database and you have not done that, when the tables are linked and normalised and data has been correctly entered you can make your queries.