A fountain pen is 12.8 yuan, which is 6.5 yuan more expensive than a ballpoint pen. How much does it cost to buy a ballpoint pen?
一支钢笔12.8元，比一支圆珠笔贵6.5元．买一支圆珠笔要用多少元？
<gadget id="calculator">12.8 - 6.5</gadget>
<output>6.3</output>

<result>6.3</result>