First Assign A Variable To Box A And Subsequently Fill The Box B & Box C
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Box A = x
Box B = x+2
Box C = 5x
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Now Using The Rest Of The Information Make An Equation Like So.
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4(x+2) = 5x + x
4x + 8 = 6x
8 = 2x
x = 4
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Now Go Back To The Top And Insert x
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Box A = x = 4
Box B = x+2 = 6
Box C = 5x = 20