Tentukan himpunan penyelesaian sistem pers. Linear 3 variabel berikut ! (Dgn caranya ya kak)

x + 3y - z = 4
x = 4 - 3y + z

3x - y + 2z = 7
3(4 - 3y + z) - y + 2z = 7
12 - 9y + 3z - y + 2z = 7
- 9y - y + 3z + 2z = 7 - 12
- 10y + 5z = - 5
- 2y + z = - 1
z = - 1 + 2y

2x + 2y + 3z = 9
2(4 - 3y + z) + 2y + 3z = 9
8 - 6y + 2z + 2y + 3z = 9
- 6y + 2y + 2z + 3z = 9 - 8
- 4y + 5z = 1
- 4y + 5(- 1 + 2y) = 1
- 4y - 5 + 10y = 1
- 4y + 10y = 1 + 5
6y = 6
y = 1

z = - 1 + 2y
z = - 1 + 2
z = 1

x = 4 - 3y + z
x = 4 - 3 + 1
x = 2