Mr. Zhang bought 5 ballpoint pens and 4 notebooks, the total cost is 23.7 yuan, and each notebook is 2.8 yuan. How much is each ballpoint pen?
张老师买了5支圆珠笔和4本笔记本，共用去23.7元，每本笔记本2.8元，每支圆珠笔多少钱？
<gadget id="calculator">2.8 * 4</gadget>
<output>11.2</output>

<gadget id="calculator">23.7 - 11.2</gadget>
<output>12.5</output>

<gadget id="calculator">12.5 / 5</gadget>
<output>2.5</output>

<result>2.5</result>