well, they bought 12 at 3,864, so each unit is 3864/12 or 322 bucks.
now, we know that those 322 are including a 30% markup, so, the orignal price have been bumped up by 30%, now, if we take say "x" to be the original price, or 100%, then 322 is he 100% + 30%, or 130%, what's "x" anyway?
[tex]\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
x&100\\
322&130
\end{array}\implies \cfrac{x}{322}=\cfrac{100}{130}\implies x=\cfrac{322\cdot 100}{130}[/tex]
