The cost of goods (purchase price) is the retail price (8/13), so the profit is the cost
商品成本(进货价)是零售价的(8/13)，那么利润是成本的多少
<gadget id="calculator">8 / 13</gadget>
<output>8/13 = around 0.615385</output>

<gadget id="calculator">1 - (8/13)</gadget>
<output>5/13 = around 0.384615</output>

<gadget id="calculator">(5/13) / (8/13)</gadget>
<output>5/8 = around 0.625</output>

<result>5/8 = around 0.625</result>