Take out (1/7) of the oil from barrel A and pour it into barrel B, then the weight of the two barrels of oil in A and B is equal, and the weight of the oil in barrel B is ((())/(())) of barrel A.
从甲桶油里取出(1/7)倒入乙桶里，则甲乙两桶油重量相等，原来乙桶里的油的重量是甲桶的((())/(()))．
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 - (1/7) - (1/7)</gadget>
<output>5/7 = around 0.714286</output>

<result>5/7 = around 0.714286</result>