4x-8=6^3 4x-8=216 4x=224 x=56

[latex]log_6(4x-8)=3\ (*)\\\\D:4x-8 > 0\to4x > 8\to x > 2\to x\in(2;\ \infty)\\\\(*)\ 4x-8=6^3\\\\4x=216+8\\\\4x=224\ \ \ \ /:4\\\\x=56\in D[/latex]