A bottle of Coke used to be 5 yuan, and it will be discounted by 20% on festivals. Now, how much is the price of each bottle?
一瓶可乐原来5元，节日一律打八折，现每瓶售价多少元．
<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>