A pile of goods weighs 150 tons, and 30 tons are used up, leaving the total ((())/(())).
一堆货物重150吨，用去了30吨，还剩总数的((())/(()))．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<result>4/5 = around 0.8</result>