How much profit does a certain retailer make from the price of a product purchased at 90 yuan at 120 yuan, and then sold at nine prices?
某个体商贩将进价90元的商品标价为120元，然后九价出售，这样他从中获利多少．
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">120 * (9/10)</gadget>
<output>108</output>

<gadget id="calculator">108 - 90</gadget>
<output>18</output>

<gadget id="calculator">18 / 90</gadget>
<output>1/5 = around 0.2</output>

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