How many grams of salt should be added to 50 grams of salt water with a salt content of 12% to obtain a salt water with a salt content of 20%.
在含盐12%的50克盐水中，要加盐多少克才能得到含盐率为20%的盐水．
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">50 * (9/10)</gadget>
<output>45</output>

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

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

<gadget id="calculator">45 / (4/5)</gadget>
<output>225/4 = around 56.25</output>

<gadget id="calculator">(225/4) - 50</gadget>
<output>25/4 = around 6.25</output>

<result>25/4 = around 6.25</result>