A basket of persimmons weighs 20 kilograms and is sold (1/5), how many kilograms are left.
一筐柿子重20千克，卖出(1/5)，还剩多少千克．
<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>

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

<result>16</result>