[tex]\bf \begin{array}{|c|ll} \cline{1-1} \textit{a\% of b}\\ \cline{1-1} \\ \left( \cfrac{a}{100} \right)\cdot b \\\\ \cline{1-1} \end{array}~\hspace{5em}\implies \stackrel{\textit{8\% of (s)ales}}{\left(\cfrac{8}{100} \right)s}\qquad \qquad \begin{cases} c=commission\\ s=total~sales \end{cases}[/tex]
[tex]\bf \stackrel{\textit{her (c)ommision is 8\% of (s)ales}}{c = \cfrac{8}{100}s\implies c=\cfrac{8s}{100}}\implies \stackrel{\textit{we know she made 2560 in commision}}{2560=\cfrac{8s}{100}\implies 256000=8s} \\\\\\ \cfrac{256000}{8}=s\implies 32000=s[/tex]
