There are 104 story books on the bookshelf. If 12 books are taken out from the first floor and placed on the second floor, then the number of books on the two shelves is equal. How many story books are there in the second shelf?
书架上共有104本故事书，如果从第一层取出12本放入第二层，那么两层书架上书的本数相等，第二层书架原有故事书多少本．
<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<gadget id="calculator">104 - 24</gadget>
<output>80</output>

<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<result>40</result>