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://img.qammunity.org/2020/formulas/mathematics/middle-school/p1apg94sa9rc2tbh4r1lb6rstcl10hofow.png)
If Kai sold 4 times more boxes of cookies than Tori we have:
![y = 4x](https://img.qammunity.org/2020/formulas/mathematics/middle-school/96eu19dmcrdu96ybk3j1mzm1ckuda2x5vu.png)
We substitute the second equation in the first:
![x + 4x = 110\\5x = 110\\x = \frac {110} {5}\\x = 22](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ecmhmkh8hyapyhwwdcv7s4oham5cs4krjy.png)
Then, Tori Chang sold 22 boxes of cookies.
![y = 4x\\y = 4 * 22\\y = 88](https://img.qammunity.org/2020/formulas/mathematics/middle-school/hftz9jf5mqc3icl95zqodt5r1gtje1v1mw.png)
Kai Chang sold 88 boxes of cookies.
Answer:
Tori Chang: 22 Boxes
Kai Chang: 88 boxes