| 
 
 
| Question 250243:  3x+3y+6z=9
 2x+y+3z=7
 x+2y-z=-10
 
 I was provided work for this problem using the matrix method. Unfortunately, I am not familiar with that method. Thanks for the help though.This is a 3-by-3 system of inequalities. In order to find the tripled pair, I need to use either the substitution of linear combination(elimination)method.
 I figured out the ordered pairs, but work doesn't match up exactly.
 Please help!
 thank you!
 Answer by Alan3354(69443)
      (Show Source): 
You can put this solution on YOUR website! 3x+3y+6z=9 --> x+y+2z=3 2x+y+3z=7
 x+2y-z=-10
 ----------
 For this problem, use eqn 1 to eliminate x from the other 2:
 x+y+2z=3 Eqn 1
 x+2y-z=-10 Eqn 3
 ---------- Subtract
 -y + 3z = 13  Eqn A
 ---------------------
 2x+y+3z=7 Eqn 2
 2x+2y+4z=6 Eqn 1 times 2
 ----------- Subtract
 -y -z = 1 Eqn B
 -y+3z = 13 Eqn A
 --------------- Subtract
 -4z = -12
 z = 3
 ------
 Sub for z, find y
 Sub for y and z, find x
 
 | 
  
 | 
 |