Let the ages of the three persons be 4x, 7x and 9x
Let the ages of the three persons 8 YEARS ago be 4x-8, 7x-8 and 9x-8
according to the question,
4x-8+7x-8+9x-8=56
20x-24=56
20x=56+24
20x=80
x=80/20
x=4
Therefore, present ages are 16,28 and 36.