After a product is reduced by 20%, the sales price is 100 yuan, and the price is reduced by 20%, what is the selling price at this time?
一种商品降低20%后，销售价为100元，再降价20%，那么此时售价为多少．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">100 * (4/5)</gadget>
<output>80</output>

<result>80</result>