SOLUTION: what is the value of x in the solution of the system? -3x-y+2z=7 2y+z=-5 3x+6y=-21 A.-4 B.3 C.-2 D.1

Algebra ->  Coordinate Systems and Linear Equations  -> Lessons -> SOLUTION: what is the value of x in the solution of the system? -3x-y+2z=7 2y+z=-5 3x+6y=-21 A.-4 B.3 C.-2 D.1      Log On


   

Question 994607: what is the value of x in the solution of the system?
-3x-y+2z=7
2y+z=-5
3x+6y=-21
A.-4
B.3
C.-2
D.1
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Add the 1st and 3rd equations,
-3x-y%2B2z%2B3x%2B6y=7-21
5y%2B2z=-14
Now multiply the second equation by -2 and add to this last equation,
-4y-2z%2B5y%2B2z=10-14
y=-4
So then,
3x%2B6%28-4%29=-21
3x-24=-21
3x=3
x=1