There are 120 grams of brine with a salt content of 15%, if it is to be converted into a brine with a salt content of 5%, how many grams of water should be added?
现有含盐15%的盐水120克，如果要把它变成含盐5%的盐水，需加水多少克？
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">5 / 100</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(3/20) / (1/20)</gadget>
<output>3</output>

<gadget id="calculator">120 * 3</gadget>
<output>360</output>

<gadget id="calculator">360 - 120</gadget>
<output>240</output>

<result>240</result>