Xiaohong brought 20 yuan to buy school supplies. She bought a pen and spent 6.8 yuan. How much money is left? (Solution of column equation)
小红带了20元钱买学习用品，她买了一枝钢笔用去6.8元，还剩多少元？(列方程解)
<gadget id="calculator">20 - 6.8</gadget>
<output>13.2</output>

<result>13.2</result>