SOLUTION: Please help me understand how to solve by substitution thank you, rob. 3X + y = -7 X

SOLUTION: Please help me understand how to solve by substitution thank you, rob. 3X + y = -7 X - Y = -5

Question 61166: Please help me understand how to solve by substitution thank you, rob.
3X + y = -7
X - Y = -5

Answer by praseena(37) (Show Source): You can put this solution on YOUR website!
Please help me understand how to solve by substitution thank you, rob.
3X + y = -7
X - Y = -5
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substitution method:
take the second equation,
x - y = -5
bring -y to the right side
==> x = -5+ y
now bring -5 to the left side
==> x + 5 = Y
which gives the value of y as x+ 5
Now substitute the value of y in the first equation, 3x + y = -7
==> 3x + x + 5 = -7
==> 4x +5 = -7
subtract 5 from both sides of the equation
==> 4x +5 -5 = -7 - 5
==> 4x = -12
now divide both sides of the equation by 4
==> 4x/4 = -12/ 4
==> x = -3

Now substitute the value x = -3 in the first equation.
==> 3*-3 + y = -7
==> -9+ y = -7
==> y = -7 + 9
==> y = 2
so the solution is
x = -3 and
y = 2

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