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April 25th, 2014, 02:40 PM   #1
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fin

3x+5y+z=40
7x+12y+2z=92

find
x+y+z
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April 25th, 2014, 02:58 PM   #2
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Write $u = x + y + z$ and $v = x + 2y$ and solve for $u$ and $v$
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April 25th, 2014, 03:27 PM   #3
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Subtracting twice the second equation from five times the first equation gives
x + y + z = 200 - 184 = 16.
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