A schoolbag is 50 yuan, sold at a 20% discount, how much is each schoolbag.
一个书包50元，按八折出售，每个书包多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">50 * (4/5)</gadget>
<output>40</output>

<result>40</result>