How many grams of water should be added to prepare 20% salt water with 5 grams of salt?
用5克盐配制含盐20%的盐水，需加水多少克．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">25 - 5</gadget>
<output>20</output>

<result>20</result>