Answer:
- A sales person must sell 10 stereos to earn the same salary with each plan.
- A sales person must sell more than 10 stereos to Plan B be better.
- A sales person must sell less than 10 stereos to Plan A be better.
Explanation:
According to the problem.
Plan A:
$250 per week.
$25 per stereo sold.
It's expressed as:
![250+25x](https://img.qammunity.org/2019/formulas/mathematics/middle-school/96kml0tcrwdi8le31x4iif5crhciwco1dv.png)
Plan B:
No salary.
$50 per stereo sold.
It's expressed as:
![50x](https://img.qammunity.org/2019/formulas/mathematics/middle-school/qv7m5ja9njulfbxur4xil9u4m111w38uu2.png)
Now, to make the same amount of money with both plans we must solve the following equality
![50x=250+25x](https://img.qammunity.org/2019/formulas/mathematics/middle-school/rzq1pf7dj7bfhcf7cbbfra21ct5ofvsdev.png)
Then, we solve for
![x](https://img.qammunity.org/2019/formulas/mathematics/college/lhtxftojjkzsmo3o2h4ilq8naohracejui.png)
![-250=25x-50x\\-250=-25x\\x=(-250)/(-25)\\ x=10](https://img.qammunity.org/2019/formulas/mathematics/middle-school/p9jsj7jq895yjb2sie0obn0wfk7g795h95.png)
So, a sales person must sell 10 stereos to earn the same salary with each plan.
On the other hand, if plan B is better than plan A, it means the following inequality is true
![B>A\\50x>250+25x\\50x-25x>250\\25x>250\\x>(250)/(25) \\x>10](https://img.qammunity.org/2019/formulas/mathematics/middle-school/d82deflbgn6k6gj9b09toq83krtnjcfdj0.png)
Therefore, if a salesperson sells more than 10 stereos, then the Plan B is better.
If plan A is better, then the following relation is true.
![A>B\\250+25x>50x\\25x-50x>-250\\-25x>-250\\x<10](https://img.qammunity.org/2019/formulas/mathematics/middle-school/zo9yye0xiqtfxfx6wf3ofcpacjuhszs7hp.png)
Therefore, if a sales person sells less than 10 stereos, then Plan A is better than Plan B.