(a)
Let $E$ be the event of numbers to be divisible by 2 or 3
$\therefore\ E = \left\{ 2,\ 3,\ 4,\ 6,\ 8,\ 9,\ 10,12 \right\}$
$\Rightarrow \ n(E) = 8\$and $n(S) = 12$
$Hence,\ required\ probability = \frac{n(E)}{n(S)}$
$= \frac{8}{12} = \frac{2}{3}$