A piece of clothing was sold at the original price on the first day, but no one bought it; the price was reduced by 10% on the second day, but still no one bought it; How much is the original price of this dress?
一件衣服第一天按原价出售，没人买；第二天降价10%，仍没人买；第三天再降价70元，终于售出，出售的价格恰好是原价的65%．这件衣服原价是几元？
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">65 / 100</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">1 - (1/10) - (13/20)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">70 / (1/4)</gadget>
<output>280</output>

<result>280</result>