SOLUTION: Solve the system by substitution. 3x-y=-7 x+y=-9

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Question 76478: Solve the system by substitution.
3x-y=-7
x+y=-9
Answer by chitra(359) About Me  (Show Source):
You can put this solution on YOUR website!
The given system of equations are:
3x - y = -7 --------------(1)
x + y = -9 --------------(2)

EQN (2) can be written as: y = -9 - x substituting this is EQN (1), we get:

3x - (-9 - x) = -7

3x + 9 + x = -7

4x = - 7 - 9

4x = - 16

x+=+-+16%2F4

==> x = - 4

Substituting this in EQN(1)

3(-4) - y = -7

==> -12 - y = -7

==> -y = -7 + 12

==> - y = 5

==> y = -5

Hence, the solutions of the given set of equations are given by:

x = -4 and y = -5 are the solutions.