Hi Larry
x^3 - 168 = [ 24(x-2)] / 2
x^3 - 168 = (24x - 48)/2
x^3 - 168 = 12x - 24
Subtract 12x - 24 to both sides
x^3 - 168 - (12x - 24) = 12xx - 24 - (12x - 24)
x^3 - 12x - 144 = 0
Now, factor the left sides
(x - 6)(x^2 + 6x + 24) = 0
Set factors equal to 0
x - 6 = 0 or x^2 + 6x + 24 = 0
x = 0 + 6 or x^2 + 6x + 24 - 0
x = 6
Answer : X = 6
Good luck !