Data:
8% commisions on the first $8000
12% commisions on a sell over $8000
Total commisions: $1480
You have the next equation for the situation: x is the sells over the $8000
[tex]\begin{gathered} C=8000(\frac{8}{100})+x(\frac{12}{100}) \\ \\ C=640+0.12x \end{gathered}[/tex]Total sells:
[tex]S=8000+x[/tex]If the total commisions are $1480:
[tex]\begin{gathered} 1480=640+0.12x \\ 1480-640=0.12x \\ 840=0.12x \\ \frac{840}{0.12}=x \\ \\ x=7000 \end{gathered}[/tex]Then, as the sells over $8000 are $7000, the total sell are the sum of 8000 and 7000: [tex]S=8000+7000=15000[/tex]Total sells: $15000