(5/9) of paint in a bucket, the total weight of the bucket is 7 kg; if (1/3) of the paint is filled, the total weight of the bucket is 4.2 kg. How many kilograms does this barrel weigh?
一个桶里(5/9)的油漆，连桶共重7千克；如果盛了(1/3)的油漆，那么连桶共重4.2千克．这个桶重多少千克？
<gadget id="calculator">7 - 4.2</gadget>
<output>2.8</output>

<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(5/9) - (1/3)</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">2.8 / (2/9)</gadget>
<output>12.6</output>

<gadget id="calculator">12.6 * (5/9)</gadget>
<output>7</output>

<gadget id="calculator">7 - 7</gadget>
<output>0</output>

<result>0</result>