The school bought 6 sets of "Children's Encyclopedia" and spent a total of 840 yuan. Each set of "Children's Encyclopedia" contains 4 books. What is the average price of each book?
学校买来6套《少儿百科全书》，一共花了840元，每套《少儿百科全书》中有4本书，平均每本书的售价是多少元？
<gadget id="calculator">4 * 6</gadget>
<output>24</output>

<gadget id="calculator">840 / 24</gadget>
<output>35</output>

<result>35</result>