There are 180 grams of salt water with a salt content of 5%. After adding how many grams of salt, the salt content will be 10%.
有180克盐水，含盐率5%，再加入多少克盐后，含盐率为10%．
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 180</gadget>
<output>18</output>

<gadget id="calculator">5 / 100</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">180 * (1/20)</gadget>
<output>9</output>

<gadget id="calculator">18 - 9</gadget>
<output>9</output>

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

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

<result>10</result>