A mobile phone whose original price is 1200 yuan is now sold at 80% of the original price, which is how much cheaper than the original price.
一种手机，原价是1200元，现在按原价的80%出售，比原价便宜了多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1_200 * (1/5)</gadget>
<output>240</output>

<result>240</result>