You can factor this treating (x+6) as the variable.
(x+6)^2 - 4(x+6) - 12 = 0
((x+6) - 6)((x+6) + 2) = 0 (factors of -12 that add to -4 are -6 and 2.)
(x)(x+8) = 0
The solutions are {-8, 0}.
(x+6)^2 - 4(x+6) - 12 = 0
((x+6) - 6)((x+6) + 2) = 0 (factors of -12 that add to -4 are -6 and 2.)
(x)(x+8) = 0
The solutions are {-8, 0}.