x + y +z = 6..........(1)
z = x + y...............(2)
x = z + 1................(3)
from equation (2) :-
x + y = -z
Subtracting this from equation (1) :-
z = -z + 6
2z = 6 so z = 3
From equation (3) :-
x = 3 + 1 = 4
And from equation (1):-
4 + y + 3 = 6
y = 6 - 7 = -1
Answer x = 4, y = -1 and z = 3.