A set of science fiction novels is 88 yuan, now 20% off, how much cheaper.
一套科幻小说88元，现打八折，便宜了多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">88 * (1/5)</gadget>
<output>88/5 = around 17.6</output>

<result>88/5 = around 17.6</result>