How much less salt than water in 20% salt water
在含盐为20%的盐水中，盐比水少多少
<gadget id="calculator">100 - 20</gadget>
<output>80</output>

<gadget id="calculator">80 - 20</gadget>
<output>60</output>

<gadget id="calculator">60 / 80</gadget>
<output>3/4 = around 0.75</output>

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