The original price of a commodity is 100 yuan, the price is first increased by 20%, and then the price is reduced by 30 yuan, how much is the reduction
一种商品，原价100元，先涨价20%，然后又降价30元，又降低了多少
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">100 * (6/5)</gadget>
<output>120</output>

<gadget id="calculator">30 / 120</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>