Two piles of apples with the same weight. After basket A sells 7 kilograms and basket B sells 19 kilograms, the remaining apples in basket A are three times that of basket B. How many kilograms of apples are there in basket B?
两堆相等数量重的苹果，甲筐卖出了7千克，乙筐卖出了19千克后，甲筐余下的苹果是乙筐的3倍，原来乙筐有多少千克苹果？
<gadget id="calculator">19 - 7</gadget>
<output>12</output>

<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">6 + 19</gadget>
<output>25</output>

<result>25</result>