A schoolbag is 20 yuan, how much is it after a 20% discount.
一个书包20元，打八折后是多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">20 * (4/5)</gadget>
<output>16</output>

<result>16</result>