the selling price is 25.60, the cost was 16.9, that means 25.6 - 16.9 = 8.7, so the item's price has been bumped up by 8.7 bucks, which is the markup, how much is that of 25.6?
worded differently, if we take 16.9(cost) to be the 100%, what is 8.7 off of it in percentage?
![\begin{array}{ccll} amount&\%\\ \cline{1-2} 16.9 & 100\\ 8.7& x \end{array} \implies \cfrac{16.9}{8.7}~~=~~\cfrac{100}{x} \\\\\\ 16.9x=870\implies x=\cfrac{870}{16.9}\implies x\approx 51.48](https://img.qammunity.org/2023/formulas/mathematics/college/spqkr91c9zsg9ps2307lq6o0uljcnaasfe.png)