The upper and lower volumes of "Story King" are 1 set, and the school reading room bought 54 sets, paying a total of 810 yuan. How much does each copy of "Story King" cost?
《故事大王》上下2本为1套，学校阅览室买了54套，共付出810元．每本《故事大王》要多少元？
<gadget id="calculator">810 / 54 / 2</gadget>
<output>15/2 = around 7.5</output>

<result>15/2 = around 7.5</result>