Add water to 12 kg of brine containing 15% salt to make the brine contain 9% salt, how many kg of water needs to be added?
在12千克含盐15%的盐水中加水，使盐水中含盐9%，需要加水多少千克．
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">12 * (3/20)</gadget>
<output>9/5 = around 1.8</output>

<gadget id="calculator">9 / 100</gadget>
<output>9/100 = around 0.09</output>

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

<gadget id="calculator">20 - 12</gadget>
<output>8</output>

<result>8</result>