This is a quotient (division) of two functions we must be concerned with the fact that division by zero is undefined.
Since g(x) is in the divisor position, it cannot equal 0.
Subtract 6 from both sides to solve.
So the domain is all real numbers except -6
Set notation {x | x ∈ R, x ≠ -6}
Interval notation (-∞,-6)∪(-6,∞)