bantuinnnn dongggg.... please..

x + y - z = - 3
x + 2y + z = 7
-------------------(+)
2x + 3y = 4 ... pers 1

x + y - z = - 3
2x + 2y + z = 5
----------------------(+)
3x + 3y = 2 ... pers 2

pers 1 & 2
2x + 3y = 4
3x + 3y = 2
-----------------(-)
- x = 2
x = - 2

subtitusi
2x + 3y = 4
2(-2) + 3y = 4
- 4 + 3y = 4
3y = 4 + 4
y = 8/3

x + y - z = - 3
- 2 + 8/3 - z = - 3 ( dikali 3)
- 6 + 8 - 3z = - 3
2 - 3z = - 3
- 3z = - 3 - 2
- 3z = - 5
z = - 5/-3
z = 5/3

hp = ( - 2, 8/3 , 5/3 )