Question

The present ages of three persons in proportions 4 7 9 . 8 year ago the sum of their age was 56 find the present age

Answer 1

If sum of their age was 56 eight years ago.
Then, presently their age is
$56 + (8 \times 3)$
which is equal to 80.
As we know proportion is 4 , 7 , 9.
Let's take a common multiple named l
Therefore the equation made is
$4l + 7l + 9l = 80$
$20l = 80$
$l = 80 \div 20$
the remaining part is in the comment.