A kind of salt water, after adding some water, the concentration of the salt water is 12%, and after adding the same amount of water, the concentration of the salt water is 8%, what is the concentration of the original salt water?
一种盐水，加入一些水后盐水的浓度为12%，再加入同样多的水后，浓度为8%，原来盐水的浓度是多少．
<gadget id="calculator">8 / 100</gadget>
<output>2/25 = around 0.08</output>

<gadget id="calculator">12 / (2/25)</gadget>
<output>150</output>

<gadget id="calculator">150 - 100</gadget>
<output>50</output>

<gadget id="calculator">100 - 50</gadget>
<output>50</output>

<gadget id="calculator">12 / 50</gadget>
<output>6/25 = around 0.24</output>

<result>6/25 = around 0.24</result>