since the selling price is 89.83 and the cost of is 76, the tax amount is 89.83 - 76 = 13.83.
if we take 76 to be the 100%, what is 13.83 off of it in percentage?
[tex]\begin{array}{ccll} amount&\%\\ \cline{1-2} 76 & 100\\ 13.83& x \end{array} \implies \cfrac{76}{13.83}=\cfrac{100}{x} \\\\\\ 76x=1383\implies x=\cfrac{1383}{76}\implies x\approx 18.20[/tex]
