Shuffle the deck and hand it to a spectator. Instruct him to shuffle/cut as well.
Take the deck back and fan it in front of the spectator. Have him remove one from the deck.
Tell him to memorize it and then place it back in the deck. Continue to shuffle as you instruct him to multiply the value of the card by two.
Once he arrives at this number, have him add 5.
After adding five, multiply the new number by five. So, if the original card was a 7, 7 X 2 = 14, 14 + 5 = 19, 19 x 5 = 95.
The spectator then selects another card from the deck and adds that value on top of the previous number, 95. If the new card is a 4, the number is 99.
Finally, have the spectator reveal the number. The trick is that whatever he says, you can identify the two chosen cards, because the first digit is the first card and the second digit is the second card. In this case, the cards were both 9's!