3 of spades
Explanation is complicating...
Divide the diagram in half, vertically. In each half, start at the top left card and move to the right, then down one row and to the left, and finally to the right, in a snakes and ladders pattern. The value of the cards in the left hand half increase alternately by 3 and 4, and the value of the cards in the right hand half increase alternately by 4 and 5. To calculate the suit of each card, start at the top left of the whole diagram and move down, then to the right one space and upwards etc. in a snakes and ladders pattern. Suits are written in order, following this path, starting with Hearts, then Clubs, Diamonds and Spades.
