The school library purchased 12 copies of "Science and Technology Series" and "Interesting Mathematics" for a total of 177.6 yuan, and each copy of "Popular Science Stories" was 6.5 yuan. (solution by equation)
学校图书馆购买《科技丛书》和《趣味数学》各12本，共用177.6元，《科普故事》每本6.5元，《趣味数学》每本多少元？(用方程解)
<gadget id="calculator">6.5 * 12</gadget>
<output>78</output>

<gadget id="calculator">177.6 - 78</gadget>
<output>99.6</output>

<gadget id="calculator">99.6 / 12</gadget>
<output>8.3</output>

<result>8.3</result>