The price of a set of furniture is 20% lower than the original price, that is to say, the current price is equivalent to the original price
一套家具售价比原来降低了20%，就是说现价相当于原价的多少
<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>

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