let x be the cost of jwellery sold by you.
The equation for option A is given by:
[tex]y=17000+\frac{8}{100}x[/tex]The equation for option B is given by:
[tex]y=21000+\frac{4}{100}x[/tex]So the equality is given by:
[tex]\begin{gathered} 17000+\frac{8}{100}x=21000+\frac{4}{100}x \\ \frac{4}{100}x=4000 \\ x=100000 \end{gathered}[/tex]Hence the sales should be 100000$ for you to make the same salary on both options.