Evaporate water from 12 kg of brine containing 9% salt to make the brine contain 15% salt, how many kg of water needs to be evaporated?
在12千克含盐9%的盐水中蒸发水使盐水中含盐15%，需蒸发水多少千克．
<gadget id="calculator">9 / 100</gadget>
<output>9/100 = around 0.09</output>

<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(9/100) / (3/20)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">12 * (3/5)</gadget>
<output>36/5 = around 7.2</output>

<gadget id="calculator">12 - (36/5)</gadget>
<output>24/5 = around 4.8</output>

<result>24/5 = around 4.8</result>