tolong bantu jawab, please!

Persamaan Linier Tiga Variabel
..
(1)
x+y =  5
y + z = 6
2x + y + z = 2 --> 2 x + (y+z) = 2
2x + (6) = 2
2x = 2 - 6 = - 4
x = -4/2 = -2

x + y = 5 --> y = 5 - x
y = 5 - (-2)
y = 7

y + z = 6 --> z = 6 - y
z = 6 -7
z = -1

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

(2)
x + y + z = -3 --> (x+y) = -3 - z
x - y = 7
2x + 2y - z = 6  --> 2 (x+ y)  - z = 6
2(-3-z) - z = 6
-6 - 2z - z = 6
-3z = 6 + 6= 12
z = 12/-3
z = -4

x + y = -3 - z
x + y = -3 -(-4) = -3 + 4
x + y = 1
.
x + y = 1
x - y = 7
......(+)...
2x = 8
x = 4
.
x + y = 1
4 + y = 1
y = 1 - 4
y = - 3

(x,y,z) = (4, -3, -4)