# math

Solve the system by substitution.
3x-3y=-12,y=-3x-12 i see its the same problem rewritten but i confused on what i should do any help would be nice

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1. If 3x - 3y = -12, then
x - y = -4. You also can rewrite the second equation to get
3x + y = -12
4x = -16 , so x = -4.
That tells you that y must be 0.

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posted by drwls
2. @drwls: The solution you provided is correct, however, it was asked that this system be solved by means of substitution.

In the second equation, it is given that y=-3x-12. Simply by replacing (i.e. substituting) y in the first equation by the value that was given for y in the second equation, we get:

3x-3(-3x-12)=-12
<=> 3x+9x+36=-12
<=> 12x = -48
<=> x = -4

since y = -3x-12, y=0

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