The school library distributes 100 books to 40 books in the third grade, and distributes the rest to three classes in the second grade. How many books does each class of the second grade get on average?
学校图书馆把100本书分给三年级40本，剩下的分给二年级三个班，二年级平均每个班分到多少本？
<gadget id="calculator">100 - 40</gadget>
<output>60</output>

<gadget id="calculator">60 / 3</gadget>
<output>20</output>

<result>20</result>