Take a deck of cards. Remove jokers
Shuffle the cards.
You must make 5 small stacks, like this:

Turn a card.
If you ever turn a  jack, queen or king place the face card on the bottom of the deck and take the next card.
In the video, you see a  4
Subtract this card from 13   (13 - 4 = 9)
Add 9 cards to this card. You now have your first stack.

Turn a  card.
If you ever turn a  jack, queen or king place the face card on the bottom of the deck and take the next card.
Example : place the queen on the bottom of the deck and take the next card (which in the video is a 5)
Subtract this card from 13  (13 - 5 = 8)
Add 8 cards to this card.
You now have the second stack.

Turn the next card (in the video you see a 5)
If you ever turn a  jack, queen or king place the face card on the bottom of the deck and take the next card.
Subtract this card from  13  (13 - 5 = 8)
Add 8 cards to this card.
You now have the third stack.

Turn the next card (in the video you see another 5)
If you ever turn a  jack, queen or king place the face card on the bottom of the deck and take the next card.
Subtract this card from 13 (13 - 5 = 8)
Add 8 cards to this card.
You now have the fourth stack.

Turn the next card (in the video you see an 8)
If you ever turn a  jack, queen or king place the face card on the bottom of the deck and take the next card.
Subtract this card from 13 (13 - 8 = 5)
Add 5 cards to this card.
You now have the fifth stack.

Put the remaining cards to the side.

Turn over all five stacks without shuffling them.

Ask the participant to remove two stacks.
Place these two removed stacks on the cards that were previously remaining.

You now have three stacks remaining.
Ask the participant to turn over 2 cards, choosing a single card from any of the three stacks.
Add these 2 cards  (example 5 + 5 = 10)
Add 10 to this total. (Always add 10 to the total of the two cards that have been turned by the participant)
Therefore 10 + 10 = 20

Take your remaining cards and count 20 cards.
Put them aside.

Count the remaining cards
In this case, there are 5 cards remaining.
Therefore your card will be a 5.

Bravo!