x-2y-z=-4 - (2)

2x+3y+z= 18 - (3)

( 1)×2:2x+2y+4z = 14-(4)

(2) x 2: 2x-4y-2z =-8 - (5)

(4)-(5) De: 6y+6z=22 Simplified De: 3y+3z = 1 1-(6)

(3)-(5) De: 7y+3z = 26 - (7)

(7)-(6) De: 4y= 15, that is, y= 15/4.

Substitute y= 15/4 into (6): 3x15/4+3z =11,and the solution is: z =-112.

Substitute y =15/4z =-112 (1): x+15/4+2× (-11).

That is, the solution of this problem is: x = 4112y =15/4z =-112.