There are several kilograms of salt water with a concentration of 8%. After evaporating part of the water, it becomes salt water with a concentration of 10%. Then add 60 kg of salt water with a concentration of 5%, and after mixing, it becomes salt water with a concentration of 7%. Q: How many kilograms of water evaporated?
有浓度为8%的盐水若干千克，蒸发去一部分水后变成浓度为10%的盐水，再加入60千克浓度为5%的盐水，混合后变成浓度为7%的盐水．问：蒸发去的水份为多少千克？
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">60 * (1/10)</gadget>
<output>6</output>

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

<gadget id="calculator">6 / (1/20)</gadget>
<output>120</output>

<gadget id="calculator">8 / 100</gadget>
<output>2/25 = around 0.08</output>

<gadget id="calculator">(1/10) - (2/25)</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">120 * (1/50)</gadget>
<output>12/5 = around 2.4</output>

<result>12/5 = around 2.4</result>