There are 15 tons of steel in the warehouse, 20% of the total is used for the first time, and 2 tons are used for the second time, how many tons are left?
仓库里有15吨钢材，第一次用去总数的20%，第二次用去2吨，还剩多少吨．
<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">15 * (4/5)</gadget>
<output>12</output>

<gadget id="calculator">12 - 2</gadget>
<output>10</output>

<result>10</result>