Step-by-step explanation:
We are told that a notebook costs $3.50 and a binder costs $6.70
If we represent the number of notebooks to be n and binders to be m
Also, we are told that she bought 4 fewer notebooks than binders
Then, we can say that
![n=m-4](https://img.qammunity.org/2023/formulas/mathematics/college/v6wm6j2jwzqsizensdssjyz42b98gbvm5m.png)
The total amount spent can be obtained using the basic principle
![Amount=cost\text{ per unit}* quantity\text{ sold }](https://img.qammunity.org/2023/formulas/mathematics/college/ryy7gt6kou5snsqp32i18pq650ast993ks.png)
Therefore
we have
![Total\text{ Amount}=3.50(n)+6.70(m)](https://img.qammunity.org/2023/formulas/mathematics/college/h4wphk1f6am6xpf2miq205r34oy3pogutj.png)
But, we have established that n = m-4
Thus
![Total\text{ amount =3.5\lparen m-4\rparen+6.7\lparen m\rparen}](https://img.qammunity.org/2023/formulas/mathematics/college/rd2l6nrbxz2vip5bevswsrx03pyo1srjqn.png)
The total amount in terms of the binders will be
![\begin{gathered} 3.5m-14+6.7m \\ 3.5m+6.7m-14 \\ 10.2m-14 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/gui6f2xtuoazx64nyqsz67h1ic6awzg4y5.png)
Thus,
we can also express the total amount in terms of the binders as
![Total\text{ amount }=10.2m-14](https://img.qammunity.org/2023/formulas/mathematics/college/a1wzj03r7rtivjyf6rda9zv60xnju18plq.png)