To solve for x, we can start by simplifying the left side of the equation:

(-1/3)^3 . x = 1/81

(-1/27) . x = 1/81

Next, we can multiply both sides of the equation by 27 to eliminate the fraction:

(-1/27) . x . 27 = (1/81) . 27

-1 . x = 27/81

-1 . x = 1/3

Finally, we can divide both sides of the equation by -1 to solve for x:

x = -1/3

Therefore, x = -1/3.