\begin{align*} P(X \ge 4) & = 1- P(x \le 3) \\ & = 1 - [ f(2) + f(3) ]\\ & = 1 - \left[ \binom{1}{1} (2/9)^2 + \binom{2}{1} (7/9)^1 \cdot (2/9)^2 \right ]\\ & = 1 - 0.1262 = 0.8738. \end{align*}