The price of a mobile phone is 1200 yuan, how much is it cheaper after 20% off.
一部手机售价1200元，八折后便宜多少元．
<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>