The current price of a schoolbag is 80 yuan, which is 20 yuan lower than in the past. What is the correct formula for the reduction by a few percent?
一种书包现价80元，比过去降低了20元，求降低了百分之几的正确列式是多少
<gadget id="calculator">20 + 80</gadget>
<output>100</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>