Question

How to do the 20th question

Answer 1

let now the age of man is 2x and son is X
after 8 yrs the ages will be 2x+8 and X+8
which are in a ratio of 7:4

so 2x+8/X+8 = 7/4
cross multiplication....
8x + 32 = 7x + 56
X = 24
the age of father is 48 and son is 24

Answer 2

Let the present age of man be 2x and be x

After 8 eight the ratio of their ages will,
7y:4y

2x+8=7y. 1equation
X+8=4y. 2equation

Then see the picture.