What is the total amount Pedro spends on 4 books

The answer depends on how much Pedro spends on each book. You did not specify so let's use an example ...

Let's say that Pedro spends $5.00 a book simply multiply 5x4 to get $20. Pedro spends $20 on 4 books.

Another example ...

Let's say that Pedro spends $4.00 a book simply multiple 4x4 to get $16.00. Pedro spends $16.00 on 4 books.

The Answer Is ... 1.75

Step-by-step explanation:

1st You Find Your Unit Rate And Then Divide That By The Amount Of Books So ... 7.00 : 4 resulting in 1.75 then you put your units. Example: 1.75 minutes