A sweater in a store is priced at 120 yuan after a 20% discount. How much is the current price cheaper than the original price?
商店一款毛衣，打八折后售价120元，现在售价比原价便宜多少钱？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">120 / (4/5)</gadget>
<output>150</output>

<gadget id="calculator">150 - 120</gadget>
<output>30</output>

<result>30</result>