The original price of a TV set is 1980 yuan, and now it is sold at a 20% discount. How much is it cheaper?
一种电视机原价是1980元，现在8折出售，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_980 * (1/5)</gadget>
<output>396</output>

<result>396</result>