Answer:
For this case we can propose an equation that will allow us to find the price of one of the books knowing the price of the other.
x: Let the variable that represents the price of the book with a green sticker
y: Let the variable that represents the price of the book with a yellow sticker
According to the statement we have:
![x=(y)/(2) -2](https://img.qammunity.org/2023/formulas/mathematics/college/653cmlkme0gsfh5yrj6ienlkbu4zeiy46j.png)
![y=2(x+2)](https://img.qammunity.org/2023/formulas/mathematics/college/c23dp8ec5g1zjm6ovte0zwdnz5wvso7lcn.png)
Finally, we can substitute the price of one of the books and clear the value of the other as the case may be.
![x=(y)/(2) -2](https://img.qammunity.org/2023/formulas/mathematics/college/653cmlkme0gsfh5yrj6ienlkbu4zeiy46j.png)