(1)X=5,(2) 9X-5Y+Z=-6 (3) X+Y=22
X+5Y-2Z=-4,9X+Y+4Z=3 X+Z=-27
4X-3Y+2Z=1; -9X+3Y-5Z=0 Y+Z=13
(1) 5+5y-2z=-4
20-3y+2z=1
25+2y=-3
y=-14
z=61/2
(2)一式减二式
-6y-3z=3
二式加三式
4y-z=3
12y-3z=9
18y=6
y=1/3
z=-5/3
x=27/28
(3)
2x+2y+2z=22-17+13
x+y+z=9
x=-6
y=36
z=-13