Answer: $\frac {e^{-0.5}}{0.8}$
Solution:-
Given, an 800 page book has 400 misprints. Therefore average rate $\lambda = 400/800 = 0.5$ misprints per page
If X follows poisson distribution, then $P(X = x) = \frac{e^{-\lambda} * \lambda^x}{x!}$, $x = 0,1,2..$
Probability of exactly 2 misprints on page 16 = $P(X=2)$
$= \frac {e^{-0.5}*(0.5)^2}{2!} = \frac {e^{-0.5}}{0.8} $ (Answer)