Buying Notebooks and Pens

Maria is planning to buy some notebooks and pens for school. Each notebook costs $2, and each pen costs $1. Maria has a budget of $20. She wants to find out how many notebooks and pens she can buy. If she buys $x$ notebooks, the relationship between the number of notebooks and the total budget can be expressed with the linear equation:

$$2x + y = 20$$

where $y$ represents the number of pens she can buy. If Maria decides to buy 5 notebooks, how many pens can she afford?