Teacher Wang has 12 yuan, just to buy a pen and 2 notebooks, if he only buys one pen, and there is 6 yuan left, do you know how much a notebook costs?
王老师有12元钱，正好买一支钢笔和2个笔记本，如果只买一支钢笔，还剩6元钱，你知道一个笔记本多少钱？
<gadget id="calculator">12 - 6</gadget>
<output>6</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<result>3</result>