SOLUTION: solve the system of equations by sustitution 3x+4y=-20 x+y=-6

Question 82890: solve the system of equations by sustitution
3x+4y=-20
x+y=-6
Answer by afphrodietic(3) (Show Source): You can put this solution on YOUR website!
let 3x+4y=-20 be the first equation
and x+y=-6 the second equation.
then, the second equation becomes x=-6-y.
plug it in the first equation.
3(-6-y)+4y=-20
-18-3y+4y=-20
-18+y=-20
y=-20+18
y=-2
and
x+(-2)=-6
x-2=-6
x=-6+2
x=-4

Then, check:
3(-4)+4(-2)=-20
-12+(-8)=-20
-12-8=-20
-20=-20
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