If a batch of commodities are sold at the fixed price, they can earn 300 yuan; if they are sold at 20% off the price, they will lose 300 yuan. Q: How much is the cost price of this batch of goods?
一批商品，如果按定价出售，可以赚300元；如果按定价的八折出售，就会亏损300元．问：这批商品的成本价是多少元？
<gadget id="calculator">300 + 300</gadget>
<output>600</output>

<gadget id="calculator">1 - 0.8</gadget>
<output>0.2</output>

<gadget id="calculator">600 / 0.2</gadget>
<output>3_000</output>

<gadget id="calculator">3_000 - 300</gadget>
<output>2_700</output>

<result>2_700</result>