There are 34 story books distributed to 3 classes, 20 to class 1, and the rest to class 2 and class 3 on average. How many books are assigned to class 2?
有34本故事书分给3个班，分给一班20本，其余平均分给二班和三班，二班分到几本？
<gadget id="calculator">34 - 20</gadget>
<output>14</output>

<gadget id="calculator">14 / 2</gadget>
<output>7</output>

<result>7</result>