Remove all dominoes that have a five or a six on them.
Use only the fifteen that remain, where the double-four is the highest.
In how many different ways may the fifteen dominoes be arranged in a straight line in accordance with the simple rule of the game that a number must always be placed against a similar number that is, a four against a four, a blank against a blank, and so on? 
Left to right and right to left of the same arrangement are to be counted as two different ways