well, the price of the printer is "x", which is incidentally the 100% of the price.
now, we know that 20.93 is 7% of "x", since that's what Shane is getting in commission anyway, what is "x" then?
[tex]\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
x&100\\
20.93&7
\end{array}\implies \cfrac{x}{20.93}=\cfrac{100}{7}\implies x=\cfrac{20.93\cdot 100}{7}[/tex]
