You bought 4 books in addition to the tote bag.
Step-by-step explanation
Suppose, the number of books you bought was

Each book costs $3.50
So, the total cost of
number of books will be:

Given that, the tote bag costs $5 and you spend a total of $19 before taxes. So, the equation will be.....

So, you bought 4 books in addition to the tote bag.