x+6≤0 x≤-6 x≤-6
x-9≤0 x≤9 x≤9
2x-7>0 2x>7 x>3,5
x+6≥0 x≥-6 x≥-6
x-9≥0 x≥9 x≥9
2x-7<0 2x<7 x<3,5<br>x∈(-∞;6]∪(3,5;9]
x-2y-z=7 x=7+2y+z
2x+3y+z=14 2(7+2y+z)+3y+z=14 14+4y+2z+3y+z=14 7y+3z=0 7y=-3z
3x-y+2z=5
y=-3z/7
3(7+2(-3z/7)+z)-(-3z/7)+2z=5 21-18z/7+3z+3z/7+2z=5 -15z/7+5z=-16
20z/7=-16
z=-16*7/20=-5,6
y=-3*(-5,6)/7=16,8/7=2,4
x=7+2*2,4+(-5,6)=11,8-5,6=6,2