Xiaohong has 12 books, and Xiaoqing has 4 books. As many books as Xiaohong wants to give to Xiaoqing, both of them have the same number of books.
小红有12本书，小青有4本书，小红要给小青多少本本书，两个人的书就同样多了．
<gadget id="calculator">12 - 4</gadget>
<output>8</output>

<gadget id="calculator">12 / 4</gadget>
<output>3</output>

<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<result>4</result>