For this case, the first thing we must do is define variables.
We have then:
x: number of days
y: total amount of M & M's
We now write the equation that models the problem:
![y = 100x - 200](https://img.qammunity.org/2019/formulas/mathematics/middle-school/swp85ze7qjh54ehzcwqjmfkvwv08ivsgwh.png)
Where,
200: initial amount
100: M & M's rate that Isabella eats per day.
Answer:
the equation is:
![y = 100x - 200](https://img.qammunity.org/2019/formulas/mathematics/middle-school/swp85ze7qjh54ehzcwqjmfkvwv08ivsgwh.png)