Which graph represents the compound inequality? n< -2 or n > =4

This would be two infinitely high planes.  The left extending infinitely to the left and stopping short of the vertical line x=-2 and the right starting just to the right of the vertical line x=4 and extending infinitely to the right.

Or you could think of it as an infinite plane excluding the infinitely high region from x=[-2,4]

Or if you are simply referring to a number line:  n=(-oo,-2)U(4,+oo)