The extracurricular group is doing experiments. Use cups to pour 5 cups of wine into a barrel. The total weight of the wine and the barrel is 870 grams. Then pour 3 cups. The total weight of the wine and the barrel is 1320 grams. How many kilograms does the barrel weigh?
课外小组在做实验．用杯子向一个桶中灌酒灌进5杯，酒和桶共重870克，再灌进3杯，酒和桶重共1320克，问桶重多少千克？
<gadget id="calculator">1_320 - 870</gadget>
<output>450</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">450 / 2</gadget>
<output>225</output>

<gadget id="calculator">225 * 3</gadget>
<output>675</output>

<gadget id="calculator">870 - 675</gadget>
<output>195</output>

<result>195</result>