A man is five times as old as his son. Four years ago, he was nine times as old. Find their present ages.

Let us assume the age of the son now = x

Then

The age of the man now = 5x

Now we have to calculate the age of the son and father 9 years ago

Age of the son 4 years ago = x - 4

Age of the man 4 years ago = 5x - 4

Then

5x - 4 = 9 (x - 4)

5x - 4 = 9x - 36

5x - 9x = - 36 + 4

- 4x = - 32

MUltiplying both sides of the equation by - 1 we get

4x = 32

x = 32/4

= 8

So the present age of the son is 8 years

Present age of the man = 5x

= 5 * 8

= 40 years

So the present age of the man is 40 years and the present age of the son is 8 years.