Question

A man is four times as old as his son after 20 years he will be twice as old as his son at that time find their present ages

Answer 1

Let the present age of man be x and the son be y. 
Now, x = 4y ---------- (1) 
After 16 years,

age of man will be x+ 16
age of son will be y +16 
Therefore, x + 16 = 2( y + 16)
x + 16 = 2y + 32
x = 2y + 16
or 4y = 2y + 16 {Using equation (a)}
2y = 16
y = 8 
Plugging back the value of y in equation (1), we get:
x = 4*8 = 32 
Hence, the present age of man is 32 years and present age of son is 8 years.



Hope it helps.

Answer 2

see your answer above