The selling price of a commodity after 20% price reduction is 720 yuan, what is the original price of this commodity.
一种商品降价20%后的售价是720元，这种商品的原价是多少元．
<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">720 / (4/5)</gadget>
<output>900</output>

<result>900</result>