For this case, the first thing we must do is define variables.
We have then:
d: number of dimes
q: number of quarters
We now write the system of equations that models the problem.
We have then:
He has a total of 30 coins:
![d + q = 30](https://img.qammunity.org/2019/formulas/mathematics/high-school/wzpywsbctkuu11boelps5ms8f15suyoqq2.png)
The toal value of Kyles coins is $ 4.80:
![0.1d + 0.25q = 4.80](https://img.qammunity.org/2019/formulas/mathematics/high-school/gnrkorgeez732kc0pth992057b4i6hl5fv.png)
Answer:
A system of equations that can be used to find the number of dimes, d, and the number of quarters, q, kyes has is:
![d + q = 30](https://img.qammunity.org/2019/formulas/mathematics/high-school/wzpywsbctkuu11boelps5ms8f15suyoqq2.png)
![0.1d + 0.25q = 4.80](https://img.qammunity.org/2019/formulas/mathematics/high-school/gnrkorgeez732kc0pth992057b4i6hl5fv.png)