The two warehouses originally had the same amount of goods. Later, Warehouse A shipped out 30 kilograms of goods, and Warehouse B brought in 50 kilograms of goods. At this time, how many kilograms of goods should be shipped from Warehouse B to Warehouse A to make the two warehouses The same amount of goods?
两个仓库原来有同样多的货物，后来甲仓库运出30千克货物，乙仓库运进50千克货物，这时再从乙仓库运出多少千克的货物给甲仓库，才能使两个仓库里的货物同样多？
<gadget id="calculator">50 + 30</gadget>
<output>80</output>

<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<result>40</result>