-√(4+2-3x+9)=-3?????

-√(4+2-3x+9)=-3  square both sides

(4+2-3x+9)= 9   simplify

15 - 3x  = 9      subtract 9 from both sides and add 3x to both sides

6 = 3x              divide both sides by 3

2 = x

And this solution will work in the original equation

15-3x=9

6=3x

x=2