So,
We know that Rachel earns 51 dollars each week.
We know that She earns one additional dollar for each book that she sells. So, we can write:
![A=51+B](https://img.qammunity.org/2023/formulas/mathematics/college/g17a3r4duychutwtti0ehhna1nntras6q0.png)
Where A is the amount of dollars and B is the number of books She sells in a week, which is equal to the number extra dollars that She earns.
If she sells 23 books, then She earns:
![\begin{gathered} A=51+23 \\ A=74 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/33nm2wsga5apd34ujiwoja61ojbtwbep8a.png)
She earns 74 dollars if she sells 23 books in a week.