A bottle of drink used to cost 5 yuan, and it will be 20% off during the holidays. Now how much does each bottle sell for?
一瓶饮料原来卖5元，节日期间一律八折，现在每瓶卖多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

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

<result>4</result>