SOLUTION: Solve the following system of equations by substitution. 5x+y=39 and y=21-3x.

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Question 343768: Solve the following system of equations by substitution.
5x+y=39 and y=21-3x.
Answer by rfer(16322) About Me  (Show Source):
You can put this solution on YOUR website!
y=21-3x
5x+y=39
5x+21-3x=39
2x=18
x=9
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y=21-3*9
y=-6
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5*9+-6=39