The shop sells a kind of football, which is treated at a 20% discount. The price of each football is 160 yuan, which is how much cheaper than the original price.
商店出售一种足球，按八折处理，每个足球售价160元，比原价便宜多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">160 / (4/5)</gadget>
<output>200</output>

<gadget id="calculator">200 - 160</gadget>
<output>40</output>

<result>40</result>