There are 20 tons of goods in a batch, 30% of which are transported for the first time, and 25% for the second time, how many tons are left in this batch of goods.
一批货物有20吨，第一次运走30%，第二次运25%，这批货物还剩下多少吨．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/5) - (1/4)</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">20 * (11/20)</gadget>
<output>11</output>

<result>11</result>