There are three concentrations of brine: A, B, and C. The concentrations are 40%, 36%, and 35%. The three kinds of brine are mixed to form 11 kg of brine with a concentration of 38.5%. The weight of C is 1/7 of that of B. Find the value of B weight.
有甲乙丙三种浓度的盐水，浓度分别是40%、36%、35%，三种盐水混合成浓度为38.5%的盐水11千克，丙的重量是乙的(1/7)，求乙的重量．
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) * 11</gadget>
<output>22/5 = around 4.4</output>

<gadget id="calculator">38.5 / 100</gadget>
<output>0.385</output>

<gadget id="calculator">11 * 0.385</gadget>
<output>4.235</output>

<gadget id="calculator">(22/5) - 4.235</gadget>
<output>0.165</output>

<gadget id="calculator">8 / 7</gadget>
<output>8/7 = around 1.142857</output>

<gadget id="calculator">(2/5) * (8/7)</gadget>
<output>16/35 = around 0.457143</output>

<gadget id="calculator">36 / 100</gadget>
<output>9/25 = around 0.36</output>

<gadget id="calculator">35 / 100</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(7/20) * (1/7)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(16/35) - (9/25) - (1/20)</gadget>
<output>33/700 = around 0.047143</output>

<gadget id="calculator">0.165 / (33/700)</gadget>
<output>3.5</output>

<result>3.5</result>