The weight ratio of oil stored in two barrels of A and B is 4:5, and 9 kg of oil is poured out of barrel A. At this time, the weight ratio of the two barrels of oil in A and B is 3:5. How many kilograms of oil is in barrel B?
甲乙两个油桶存油重量比是4：5，从甲桶倒出9千克油，这时甲乙两桶油重量的比是3：5，乙桶有油多少千克？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(4/5) - (3/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">9 / (1/5)</gadget>
<output>45</output>

<result>45</result>