Dissolve 2 kg of salt in 8 kg of water to obtain 10 kg of brine. If you want to make the brine contain salt (1/4), should you add salt or water to the brine? How much?
把2千克盐溶解于8千克水中，得到10千克盐水，如果要使盐水中含盐(1/4)，往盐水中加盐还是加水？加多少？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

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

<gadget id="calculator">8 / (3/4)</gadget>
<output>32/3 = around 10.666667</output>

<gadget id="calculator">(32/3) - 10</gadget>
<output>2/3 = around 0.666667</output>

<result>2/3 = around 0.666667</result>