For this case, we propose a system of two equations with two unknowns.
Let:
x: The variable that represents the number of biscuit boxes sold by Tori Chang
y: The variable that represents the number of biscuit boxes sold by Kai Chang
Between the two they sold 110 boxes of cookies:
![x + y = 110](https://tex.z-dn.net/?f=x%20%2B%20y%20%3D%20110)
If Kai sold 4 times more boxes of cookies than Tori we have:
![y = 4x](https://tex.z-dn.net/?f=y%20%3D%204x)
We substitute the second equation in the first:
![x + 4x = 110\\5x = 110\\x = \frac {110} {5}\\x = 22](https://tex.z-dn.net/?f=x%20%2B%204x%20%3D%20110%5C%5C5x%20%3D%20110%5C%5Cx%20%3D%20%5Cfrac%20%7B110%7D%20%7B5%7D%5C%5Cx%20%3D%2022)
Then, Tori Chang sold 22 boxes of cookies.
![y = 4x\\y = 4 * 22\\y = 88](https://tex.z-dn.net/?f=y%20%3D%204x%5C%5Cy%20%3D%204%20%2A%2022%5C%5Cy%20%3D%2088)
Kai Chang sold 88 boxes of cookies.
Answer:
Tori Chang: 22 Boxes
Kai Chang: 88 boxes