Teacher Wang spent a total of 30.5 yuan on notebooks and pens, of which 12 yuan was spent on notebooks. How much did you spend on the pen?
王老师买笔记本和钢笔一共花了30.5元，其中笔记本用去12元．买钢笔花了多少钱？
<gadget id="calculator">30.5 - 12</gadget>
<output>18.5</output>

<result>18.5</result>