Poker hand: 5 cards. Deck: 52 cards.
$$\begin{pmatrix}
52\\ 5
\end{pmatrix}$$
There is 4 aces, number of outcomes to pick one ace:
$$4*\begin{pmatrix}
52\\ 1
\end{pmatrix}$$
And at last, number of outcomes to fill slots for other 4 cards.
49 because, we don't won't to pick 3 remaining aces.
$$\begin{pmatrix}
49\\ 4
\end{pmatrix}$$
Result:
$$\frac{
4*
\begin{pmatrix}
52\\ 1
\end{pmatrix}
*
\begin{pmatrix}
49\\ 4
\end{pmatrix}
}{
\begin{pmatrix}
52\\ 5
\end{pmatrix}
}$$
Can somebody explain why this answer is not correct?