Answer:
![B = (31.5)/(5.25)= 6](https://img.qammunity.org/2021/formulas/mathematics/college/7hlpz79x6pezlfmwbquqjse9vk3ryw7brs.png)
![H = 18-6= 12](https://img.qammunity.org/2021/formulas/mathematics/college/nc6mizr7nj7ckhmq6f430ffsk6ubzbsocm.png)
So then Mark purchased 12 Hamburgers and 6 packages of buns
Explanation:
For this case we can define the following notation:
B represent the number of packages buns
H represent the number of hamburgers
And from the information given we can set up the conditions into the following equations:
(1) represent the total cost
(2) represent the total number of items
Solving H from equation (2) we got:
(3)
And replacing equation (3) into equation (1) we got:
![6.75 (18-B) +1.5 B =90](https://img.qammunity.org/2021/formulas/mathematics/college/tbcoqzp9f4e8lwt0i8obj6la0epl63l62d.png)
And dsitributing the terms we have:
![121.5 -6.75 B +1.5 B =90](https://img.qammunity.org/2021/formulas/mathematics/college/49xu6z4cydng2q7bs80uu2h58wmdq99b8j.png)
And solving for B we got:
![121.5-90 = 5.25 B](https://img.qammunity.org/2021/formulas/mathematics/college/dk6uruidvbeaejcn58nyhhtgu0okd6nyoy.png)
And dividing by 5.25 we got:
![B = (31.5)/(5.25)= 6](https://img.qammunity.org/2021/formulas/mathematics/college/7hlpz79x6pezlfmwbquqjse9vk3ryw7brs.png)
And replacing the value of B into equation (3) we got:
![H = 18-6= 12](https://img.qammunity.org/2021/formulas/mathematics/college/nc6mizr7nj7ckhmq6f430ffsk6ubzbsocm.png)
So then Mark purchased 12 Hamburgers and 6 packages of buns