The selling price of a bicycle after a 20% discount is 180 yuan. How much is the current price of this bicycle cheaper than the original price?
一辆自行车打八折后的售价是180元，这辆自行车的现价比原价便宜多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">180 / (4/5)</gadget>
<output>225</output>

<gadget id="calculator">225 - 180</gadget>
<output>45</output>

<result>45</result>