Let c represent amount of commission and s represent amount of sales.
We have been given that Lee sells electronics. He earns a 5% commission on each sale he makes.
A. We are asked to find the constant of proportionality.
First of all, we will write our given equation as direct proportion. We know that two proportional quantities are in form
, where y is directly proportional to x and k represents constant of proportionality.
We can represent our given information in an equation as:
![c=(5)/(100)s](https://img.qammunity.org/2021/formulas/mathematics/middle-school/894824x8a4rpcs8a7thm4a14c9stsmfto9.png)
![c=0.05s](https://img.qammunity.org/2021/formulas/mathematics/middle-school/bffbn72l9c2m51i3oxpdkbpdtiuas2egua.png)
Therefore, constant of proportionality is
.
B. To find amount of electronics sold by Lee, we will substitute
in our equation an solve for s as:
![100=0.05s](https://img.qammunity.org/2021/formulas/mathematics/middle-school/r512hbvsp3yzwp1v0n5xtj2a7ewvnmjvma.png)
![(100)/(0.05)=(0.05s)/(0.05)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/tlsqkaa42agegop0053bppy7tzq5kgm8ca.png)
![2000=s](https://img.qammunity.org/2021/formulas/mathematics/middle-school/93ep57euavzsdhwptjgxlp5520ajnrymlg.png)
Therefore, Lee must sell $2000 of electronics to make $100 commission.