carilah nilai x-y+z dari spltv berikut 2x+y+z=12 x+2y-z=3. 3x-y+z=11

misal : x + 2y - z = 3
x = -2y + z + 3

2x + y + z = 12
2(-2y + z + 3) + y + z = 12
-4y + 2z + 6 + y + z = 12
-3y + 3z = 6 ... pers 1

3x - y + z = 11
3(-2y + z + 3) -y + z = 11
-6y + 3z + 9 -y + z = 11
-7y + 4z = 2 ... pers 2

pers 1 & 2
-3y + 3z = 6. |X4|
-7y + 4z = 2. |X3|
-12y + 12z = 24
-21y + 12z = 6
-----------------------(-)
9y = 18
y = 2
-3y + 3z = 6
-3(2) + 3z = 6
-6 + 3z = 6
3z = 12
z = 4
x = -2y + z + 3
x = -2(2) + 4 + 3
x = 3
nilai x - y + z = 3 - 2 + 4 = 5