1 fountain pen costs 5 yuan more than 3 ballpoint pens. 15.5 yuan per pen, how much is each ballpoint pen?
1支钢笔比3支圆珠笔贵5元．每支钢笔15.5元，每支圆珠笔多少元？
<gadget id="calculator">15.5 - 5</gadget>
<output>10.5</output>

<gadget id="calculator">10.5 / 3</gadget>
<output>3.5</output>

<result>3.5</result>