Now their ages are in the ratio of 4:7:9
Let the common multiple be x
Therefore their ages are
4x, 7x and 9x
8 years ago, their ages were 4x-8, 7x-8, 9x-8
Therefore adding them,
(4x-8) + (7x-8) + (9x-8) = 56
20x = 56+24 = 80
Hence x = 4
Therefore their present ages are:
4x = 16
7x = 28
9x = 36