Add 30 kg of water to 20% brine to make the concentration 15%, and how many kilograms of salt are added to make the concentration 25%.
在浓度为20%的盐水中加入30千克水，浓度变为15%，再加入多少千克盐，浓度变为25%．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) - 0.15</gadget>
<output>0.05</output>

<gadget id="calculator">4.5 / 0.05</gadget>
<output>90</output>

<gadget id="calculator">90 + 30</gadget>
<output>120</output>

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

<gadget id="calculator">1 - (3/20)</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">(17/20) / (3/4)</gadget>
<output>17/15 = around 1.133333</output>

<gadget id="calculator">120 * (17/15)</gadget>
<output>136</output>

<gadget id="calculator">136 - 120</gadget>
<output>16</output>

<result>16</result>