The school bought 54 science and technology books, 9 of which were used by teachers. Divide the remaining books equally among 5 classes, how many books are assigned to each class.
学校买来54本科技书，其中9本给老师用．把剩下的书平均分给5个班，每班分到多少本．
<gadget id="calculator">54 - 9</gadget>
<output>45</output>

<gadget id="calculator">45 / 5</gadget>
<output>9</output>

<result>9</result>