数学题：一件商品按成本提高30%，换季又打八折，降价后每件卖104元，这种商品卖出一件是赔是赚？赔或赚多少钱？[解方程，由“Smile-资优网”提出]

数学题解答：设成本为x元。

(1+30%)x × 80% =104

1.04 x =104

x=100

成本是100元，卖104元。所以是赚了，赚了：104-100=4（元）

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