Add 2 kilograms of water to 30% sugar water, the concentration becomes 20%, how many kilograms of sugar are added, the concentration becomes 28%?
在浓度为30%的糖水中加入2千克水，浓度变为20%，再加入多少千克糖，浓度变为28%？
<gadget id="calculator">6 - 1.2</gadget>
<output>4.8</output>

<gadget id="calculator">72 / 100</gadget>
<output>18/25 = around 0.72</output>

<gadget id="calculator">4.8 / (18/25)</gadget>
<output>6.666667</output>

<gadget id="calculator">6.666667 - 6</gadget>
<output>0.666667</output>

<result>0.666667</result>