The price of a fountain pen is 18.6 yuan, which is 10.9 yuan more expensive than a ballpoint pen. How much is a ballpoint pen? (column equation solution)
一枝钢笔的价钱是18.6元，比一枝圆珠笔贵10.9元，一枝圆珠笔多少元？(列方程解答)
<gadget id="calculator">18.6 - 10.9</gadget>
<output>7.7</output>

<result>7.7</result>