Algebra help... 3x^2-6x-24=0

Solve by completing the square, this is what I did:
3x^2-6x-24=0
x^2-3x-8=0
x^2-3x=8
x^2-3x-3/2=9 1/3
What do I do next lol? Or did i do something wrong?

You messed up division by 3. It'd be x^2-2x-8=0. Then you just continue. x^2-2x=8, (x-1)^2=9, x^2-2x-8=0 (oddly enough, we got the same quadratic), (x-4)(x+2)=0, x=-2 or x=4

First correct step two
x^2 - 2x - 8 = 0
x^2 - 2x + (2/1)^2 - 8 = (2/1)^2
(x - 1)^2 - 8 = 1
(x - 1)^2 = 9
x - 1 = 3 or x - 1 = -3
x - 4 or x = -2

3x^2-6x-24=0
x^2-2x = 8
x^2 - 2x + 1 = 8 + 1
(x - 1)^2 = 9
x - 1 = ±3
x = -2 , 4