Answer:
![L+S=413----------------1\\\\1.2L+3S=1068---------2](https://img.qammunity.org/2021/formulas/mathematics/high-school/5s4y6ltbfqpqerwzjl9y23jd4q5jk7sb05.png)
Explanation:
Step one:
given data
A vendor sold a total of 413 fries
Large fries cost $1.20 and souvenir sodas cost $3
let L be the number of large fries sold and S be the number of souvenir sodas
so
L+S=413
and
1.2L+3S=1068
Therefore the system of equation is
![L+S=413----------------1\\\\1.2L+3S=1068---------2](https://img.qammunity.org/2021/formulas/mathematics/high-school/5s4y6ltbfqpqerwzjl9y23jd4q5jk7sb05.png)