Domino Concentration Game

This game "Domino Concentration" is basically a memory test. The goal is to flip all tiles in pairs so that their total number is 12. If the flipped tiles do not add up to 12, they are flipped face down again. The player may then flip any two tiles again. The tiles are only removed in pairs if the total number of tiles is 12. Try to flip all tiles in the game Domino Concentration in the least number of attempts.