Cards are drawn one-by-on e at random from a well-shuffled pack of 52 playing cards until 2 aces are obtained from the first time. The probability that 18 draws are required for this is

18 draws are required for 2 aces. This means in the first 17 draws, there is one ace and 16 other cards, and 18th draw produces an ace. So, the required probability is      48C16×4C1 52C17×335=56115925