Mark M. answered 04/10/20
Retired math prof. Very extensive Precalculus tutoring experience.
Since x is in quadrant 2, cosx is negative. cosx = -√[1-(1/3)2] = -2√2/3
sin(x + π/6) = (sinx)cos(π/6) + (cosx)sin(π/6) = (1/3)(√3/2) - (2√2/3)(1/2) = (√3 - 2√2) / 6