If a product is sold at a 10% discount, the profit can be 100 yuan, and if it is sold at a 20% discount, the profit can be 78 yuan. What is the cost of the product?
某商品若打九折出售，就可以盈利100元，若打八折出售，可以盈利78元，则该商品的成本是多少元．
<gadget id="calculator">100 - 78</gadget>
<output>22</output>

<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(9/10) - (4/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">22 / (1/10)</gadget>
<output>220</output>

<gadget id="calculator">220 * (9/10)</gadget>
<output>198</output>

<gadget id="calculator">198 - 100</gadget>
<output>98</output>

<result>98</result>