solve the system?

Question

|x+2y-2z=-1|
|x+3y+z=10|
|2x+6y+2z=20|


possible answers:

(8c-23, -3c+10, c) for any real number c
(8c-22, -3c+10, c) for any real number c
(8c-22, -3c+11, c) for any real number c
(8c-23, -3c+11, c) for any real number c

Answer 1

(8c-22, -3c+11, c) for any real number c

Answer 2

the third eq is a multiple of the second eq. so you have 2 eq and 3 unknown.
by subtracting the sec eq from first
x+2y-2z=-1
x+3y+z=10
-------------------
0-y-3z=-11
y=11-3z

then subtract 3 times the first eq from the third
2x+6y+2z=20
3x+6y-6z=-3
---------------------
-x+0+8z=23
x=8z-23

answer is the 4th on the list