Put 120 books on average on two bookshelves, each shelf has 5 layers, how many books are placed on each layer on average?
把120本书平均放在两个书架上，每个书架有5层，平均每层放多少本书？
<gadget id="calculator">120 / 2 / 5</gadget>
<output>12</output>

<result>12</result>