Use a deck of 52 cards and shuffle them well.
Hold the deck of cards face down.
Turn over the top card and place it face up on the table. 

Add to the top of this card as many more cards as needed to reach 10.
Face cards count as 10, leave them as a pile.

Example :
In the video, the first card is an 8.
Add  2 cards to make the total 10.
The second card in the video is a 7.
Add 3 cards to make the total 10.
Continue making stacks until all the deck is exhausted. 
If there are not enough cards to complete a final stack, keep that incomplete stack in your hand. 

Choose any three stacks that contain four cards or more.
Turn these stacks face down.
Randomly pick up the stacks remaining and add them to the cards (if any) in your hand. 

Ask the participant to turn over the top card of any two piles. 
Add their values together.

In the video the total is 2.

Discard that many cards from those in your hand.
Now discard 19 more cards.

Count the remaining cards in your hand. 
The total amount of cards left in your hand will be the top card of the remaining stack.

Magic!