For the system x+y+z=6x + y + z = 6x+y+z=6, 2x+2y+2z=122x + 2y + 2z = 122x+2y+2z=12, and x+2y+z=7x + 2y + z = 7x+2y+z=7, how many solutions exist?
None
Exactly one
Infinitely many
Two