There are 20 tons of steel in the warehouse, 20% of the total is used, how many tons are left?
仓库里有20吨钢材，用去总数的20%，还剩下多少吨？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">20 * (4/5)</gadget>
<output>16</output>

<result>16</result>