Each fountain pen is 3 yuan, and Xiaogang now has 22 yuan, so he can buy 8 fountain pens with as many yuan as he needs.
每支水笔3元，小刚现在有22元，还需要多少元，就可以买8支水笔．
<gadget id="calculator">3 * 8</gadget>
<output>24</output>

<gadget id="calculator">24 - 22</gadget>
<output>2</output>

<result>2</result>