How much less salt than water in salt water with a salt content of 20%
在含盐量是20%的盐水中，盐比水少多少
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5) - (1/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

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

<result>3/4 = around 0.75</result>