There are 300 grams of salt water with a salt content of 20%, how many grams of salt should be added to increase the salt content to 25%.
有含盐率为20%的盐水300克，要把含盐率提高到25%，应再加入多少克盐．
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) * 300</gadget>
<output>75</output>

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

<gadget id="calculator">300 * (1/5)</gadget>
<output>60</output>

<gadget id="calculator">75 - 60</gadget>
<output>15</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">15 / (3/4)</gadget>
<output>20</output>

<result>20</result>