On this problem, I think I'm more confused about the possible answers than the problem itself. How would you suggest I go about it?

Solve the system

{x+2y-2z=-1

{x+3y+z=10

{2x+6y+2z=20

solutions:

a. (8c-23, -3c+10, c) for any real number c.

b. (8c-22, -3c+10, c) for any real number c.

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

d. (8c-23, -3c+11, c) for any real number c.