There are two horses and a pair of saddles, the price of a white horse with a saddle is 800 yuan, the price of a black horse with a saddle is 600 yuan, and the price of two horses is 1,000 yuan, so the price of a pair is based on the price.
有两匹马和一副鞍，白马配鞍售价800元，黑马配鞍售价600元，两匹马售价1000元，那么一副按售价多少元．
<gadget id="calculator">600 - 1_000</gadget>
<output>-400</output>

<gadget id="calculator">800 + (-400)</gadget>
<output>400</output>

<gadget id="calculator">400 / 2</gadget>
<output>200</output>

<result>200</result>