Add some water to the salt water containing 60% salt and turn it into salt water containing 30% salt. At this time, the weight of the salt water is 300 grams. How many grams of salt water are there?
把含盐60%的盐水中，加入一些水后变成了含盐30%的盐水，这时盐水的重量是300克，原来有盐水多少克？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/10) / (3/5)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">300 * (1/2)</gadget>
<output>150</output>

<result>150</result>