​ What is the exact value of the trigonometric expression in simplest form?

tan (2pi / 3)  = - tan (60°)   = -√3

cos ( 11 pi / 6 )  =  cos (30°)  =  √3 / 2

So....substituting, we have

-√3 +  4 (√3 / 2 )  =

-√3  + 2√3  =

√3