How many grams of water should be evaporated to obtain 20% salt water by distilling water from 80 grams of salt water containing 16% salt?
要从含盐16%的80克盐水中蒸去水分，制成含盐20%的盐水，应蒸去多少克水．
<gadget id="calculator">16 / 100</gadget>
<output>4/25 = around 0.16</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(4/25) / (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">80 * (4/5)</gadget>
<output>64</output>

<gadget id="calculator">80 - 64</gadget>
<output>16</output>

<result>16</result>