There are two barrels of oil, A and B, and the weight of the oil in barrel B is more than that in barrel A (1/5). The oil is 21 kilograms more, how many kilograms of oil is in barrel A?
有甲乙两豆桶油，乙桶油的重量比甲桶油多(1/5)，如果从甲桶油中取出(1/4)放到乙桶中，这时，乙桶油比甲桶油多21千克，求甲桶油原来有多少千克？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 + (1/5) + (1/4)</gadget>
<output>29/20 = around 1.45</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(29/20) - (3/4)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">21 / (7/10)</gadget>
<output>30</output>

<result>30</result>