The price of a commodity is 81 yuan after a 10% discount. What is the original price?
一件商品，打9折后售价是81元，原价是多少元．
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">81 / (9/10)</gadget>
<output>90</output>

<result>90</result>