You do (5sqrt(11))^2 + 11^2 = 396. So we find the hypotenuse = sqrt(396) = 6sqrt(11).
Since its in the third quadrant 5sqrt(11) is negative so we have sin(x) = -5sqrt(11)/6sqrt(11). The sqrt(11)'s cancel and we have -5/6.
A) -5/6 is the answer.
