There are 50 kilograms of brine with 15% salt content, how many kilograms of water can be evaporated to increase the concentration by 5%.
有含盐15%的盐水50千克，蒸发多少千克的水后可将浓度提高5%．
<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>1/5 = around 0.2</output>

<gadget id="calculator">(3/20) / (1/5)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">50 * (3/4)</gadget>
<output>75/2 = around 37.5</output>

<gadget id="calculator">50 - (75/2)</gadget>
<output>25/2 = around 12.5</output>

<result>25/2 = around 12.5</result>