Two barrels of oil, A and B, weigh 50 kilograms in total. Pour 20% of barrel B into barrel A. Now the mass ratio of oil in barrels A and B is 3:2. How many kilograms of oil are in barrel B?
甲乙两桶油共重50千克，把乙桶的20%倒到甲桶里，现在甲乙两桶油的质量比是3：2．乙桶里原来有油多少千克．
<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(2/5) / (4/5)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">50 * (1/2)</gadget>
<output>25</output>

<result>25</result>