Question

Solving systems of equations with three variables?
What is the solution to the system?
1] x+y+z=-3
2] 3y-z=4
3] 2x-y-2z=-5

Answer 1

equation 2 only has two variables so use it to solve for z
z = (3y-4)

now substitute (3y-4) for z in the other 2 equations

x+y+(3y-4)=-3
2x-y-2(3y-4)=-5

1 x + 4 y = 1
2 x - 7 y = -13

2 x + 8 y = 2
2 x - 7 y = -13
----------------
0 x +15 y = 15

y = 1
etc