You show a red and blue deck.
The red deck is shuffled by a spectator, and you talk about bridge and each player gets 13 cards in bridge. The spectator counts down 13 cards to the table.
Now two spectators are thinking of a card. One red and one black card.
The cards are split up in red and black, and each spectator adds up there cards and say the number to you. You now say to the spectators, that you earlier today you placed 2 cards in a blue deck at exact at their numbers. Both spectators are now counting to their number in the blue deck. Both cards will show up at their number, and these are the cards the spectators are thinking of.
