A glass of salt water, after adding a certain amount of water for the first time, the percentage of salt in the salt water becomes 15%; the same amount of water is added for the second time, and the percentage of salt in the salt water becomes 12%; the same amount is added for the third time What is the percentage of table salt in the brine?
一杯盐水，第一次加入一定量的水后，盐水的含盐百分比变为15%；第二次又加入同样多的水，盐水的含盐百分比变为12%；第三次再加入同样多的水，盐水的食盐百分比将变为多少．
<gadget id="calculator">4 / 1</gadget>
<output>4</output>

<gadget id="calculator">1 / 1</gadget>
<output>1</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">4 * (3/20)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">3 + 1 + 1 + 1</gadget>
<output>6</output>

<gadget id="calculator">(3/5) / 6</gadget>
<output>1/10 = around 0.1</output>

<result>1/10 = around 0.1</result>