Answer:
x = -2, y = -1, z = 1
Explanation:
From (3), z = 2x + 5
From (2) y = (x - 2)/4
Sub them into (1):
5x - 6*(x - 2)/4 + 3(2x + 5) = -1
5x - 3x/2 + 3 + 6x + 15 = -1
19x/2 = -19
x/2 = -1
x = -2
y = (x - 2)/4 = (-2-2)/4 = -1
z = 2x + 5 = 2(-2) + 5 = 1