Question 135395
The problem is: 
y=4-3x 
3x+y=5
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Substitute 1st into 2nd to get:
3x+4-3x = 5
4 = 5
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That is a contradiction which resulted from thinking
that the variables in one equation were the same as 
the variables in the other.
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The system is "inconsistent"; it has no solution
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If you graphed the two equation you would get
parallel lines, which share no (x,y) point.
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Cheers,
Stan H.