63 ( 97 ) 49
56 ( 73 ) 24
? ( 36 ) 54
What number should replace the question mark?
27
In the first row divide both numbers by 7 to obtain the digits in the brackets; in the second row divide by 8, and obtain the digits in the brackets. In last row divide by 9, and obtain the digits in the brackets.
27 / 9 = 3