How many grams of water is added to 100 grams of salt water containing 13% salt will become salt water containing 10% salt.
含盐13%的盐水100克，加入多少克水就变成含盐10%的盐水．
<gadget id="calculator">13 / 100</gadget>
<output>13/100 = around 0.13</output>

<gadget id="calculator">100 * (13/100)</gadget>
<output>13</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">13 / (1/10)</gadget>
<output>130</output>

<gadget id="calculator">130 - 100</gadget>
<output>30</output>

<result>30</result>