Bottle A contains 900 grams of 20% salt water, and bottle B contains 600 grams of 45% salt water. Now pour several grams of salt water from bottle B into bottle A. After mixing, pour another weight of salt water from bottle A back into bottle B. bottle, so that A and B have the same weight of the two bottles of salt water. Now the concentration of brine in bottle B is 6% higher than that in bottle A. How many grams does the second poured brine weigh?
甲瓶有20%浓度的盐水900克，乙瓶有45%浓度的盐水600克，现将乙瓶若干克盐水倒入甲瓶，混合后，再由甲瓶倒回另一重量的盐水到乙瓶，使甲、乙两瓶盐水的重量一样．现在乙瓶盐水的浓度比甲瓶的高6%，问第二次倒入的盐水重多少克？
<gadget id="calculator">900 + 600</gadget>
<output>1_500</output>

<gadget id="calculator">1_500 / 2</gadget>
<output>750</output>

<gadget id="calculator">750 - 600</gadget>
<output>150</output>

<gadget id="calculator">350 + 150</gadget>
<output>500</output>

<result>500</result>