A barrel of oil weighs 1200 grams in total. After half of it is used up, the weight of the barrel is 700 grams. What is the weight of the barrel?
一桶油连桶共重1200克，用去一半后连桶重700克，桶重多少克．
<gadget id="calculator">1_200 - 700</gadget>
<output>500</output>

<gadget id="calculator">500 * 2</gadget>
<output>1_000</output>

<gadget id="calculator">1_200 - 1_000</gadget>
<output>200</output>

<result>200</result>