There is 20 kilograms of oil in barrel A, and 12 kilograms of oil in barrel B. How many kilograms of oil is poured into barrel A into barrel B, and the two barrels of oil weigh the same?
甲桶油有20千克，乙桶油有12千克，甲桶向乙桶里面倒入多少千克油后，两桶油一样重？
<gadget id="calculator">20 + 12</gadget>
<output>32</output>

<gadget id="calculator">32 / 2</gadget>
<output>16</output>

<gadget id="calculator">20 - 16</gadget>
<output>4</output>

<result>4</result>