A piece of clothing, after increasing the price by 20 yuan, then reduced it by 10%, and finally sold it for 99 yuan. How much is the original price of this dress?
一件衣服，加价20元后，再降低10%，结果卖99元．这件衣服原价多少元？
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">99 / (9/10)</gadget>
<output>110</output>

<gadget id="calculator">110 - 20</gadget>
<output>90</output>

<result>90</result>