A barrel of oil weighs 20 kilograms, how many kilograms are left after pouring out (3/5).
一桶油重20千克，倒出(3/5)后还剩多少千克．
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">20 * (2/5)</gadget>
<output>8</output>

<result>8</result>