A kind of salt water weighs 200 grams, and the weight of salt accounts for 20% of the weight of the salt water. After adding some water, the weight of salt accounts for 12.5% of the weight of the salt water. How many grams of water were added?
一种盐水重200克，盐的重量占盐水的20%，加了一些水后，盐的重量占盐水重量的12.5%．加了多少克水？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">12.5 / 100</gadget>
<output>0.125</output>

<gadget id="calculator">(1/5) / 0.125</gadget>
<output>1.6</output>

<gadget id="calculator">200 * 1.6</gadget>
<output>320</output>

<gadget id="calculator">320 - 200</gadget>
<output>120</output>

<result>120</result>