Swimmer 2 second and swimmer 5 among the medals

Six equally matched swimmers, numbered $1$ to $6$, race each other, so every finishing order is equally likely. What is the probability that swimmer $2$ takes second place and swimmer $5$ finishes somewhere in the top three?

$\tfrac{1}{15}$. Swimmer $2$ is second with probability $\tfrac16$. Given that, swimmer $5$ is equally likely to occupy any of the five other places, two of which are in the top three, giving $\tfrac16\cdot\tfrac25=\tfrac1{15}$.