The school library purchased 3 sets of "Encyclopedia", 6 books in each set, and spent a total of 324 yuan. How much is the average price for each book?
学校图书室购进3套《百科全书》，每套6本，共花了324元，平均每本多少元？
<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<gadget id="calculator">324 / 18</gadget>
<output>18</output>

<result>18</result>