There are 170 grams of salt water with a concentration of 10%. After adding how many grams of salt, the concentration of salt water will be 15%.
有浓度为10%的盐水170克，加入多少克盐后，盐水的浓度为15%．
<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">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">1 - (3/20)</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">(9/10) / (17/20)</gadget>
<output>18/17 = around 1.058824</output>

<gadget id="calculator">170 * (18/17)</gadget>
<output>180</output>

<gadget id="calculator">180 - 170</gadget>
<output>10</output>

<result>10</result>