This type of mathematical card trick is an interesting one for viewers, and it normally requires three people who select one card each from the total of 52 without showing it to you. As a performer, you have to tell them to memorize the number of the three selected cards before they are mixed with others in three separate piles. After this, the cards are placed on a table one by one in such a way that one card is placed face up and the others are placed with their face down. This continues till all the cards are placed face up except for three, which will remain behind. And they will be those selected by the spectators. There is a very simple method involved in this trick.
Once the cards are placed in the above order, make several cuts and shuffles of the piles separately. After that, put the last pile on the middle pile, and then both of them on the first pile, ensuring that the selected cards are mixed in the deck.
Now first 4 cards that come on top of the deck should be picked and put at the bottom. After that, start placing all cards one by one in a way that when placed, one card should be facing up and the other is face down. You may ask the spectators to STOP you when they see their cards, which they normally won't.