Answer
$pH \approx 5.4$
No, that number doesn't make sense because NaOH is a base.
We normally disconsider the concentration of $[H^+]$ and $[OH^-], which we can't do in this case.
Work Step by Step
1. Find the pH, by the normal formula:
$pOH = -log[OH^-]$
$pOH = -log(2.5 \times 10^{-9})$
$pOH = 8.6$
$pH = 14 - pOH$
$pH = 5.4$
2. Since $NaOH$ is a base, we expect that the pH will be higher than 7, so 5.4 doesn't make sense.
3. If we consider the concentration of $[OH^-]$ in pure water:
$pOH = -log((2.5 \times 10^{-9})+(10^{-7}))$
$pOH = 6.99$
$pH = 7.01$
And that number is compatible with a base solution.