bookshelf has two floors, 42 books are placed on the first floor, and 30 books are placed on the second floor. Now add the same number of books to the two floors, so that there are 96 books in total on the two floors. Add a few books?
一个书架有两层，第一层放着42本书，第二层放着30本书，现在分别给两层添上同样多的书，使两层一共有96本书，问这两层各要添几本书？
<gadget id="calculator">42 + 30</gadget>
<output>72</output>

<gadget id="calculator">96 - 72</gadget>
<output>24</output>

<gadget id="calculator">24 / 2</gadget>
<output>12</output>

<result>12</result>