The original price of a product is 3,000 yuan, and now there is a 20% discount promotion. After the event is over, how many percent will the price be raised to restore the original price? (need formula)
一件商品的原价是3000元，现在8折促销，活动结束后，再提价百分之几才能恢复原价？(要式子)
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 * (4/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 / (4/5)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">(5/4) - 1</gadget>
<output>1/4 = around 0.25</output>

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