Father-Son Age Puzzle

Let the current age of son be $x$ years.
Therefore, Current age of father = $9x$ years.

After 3 years.
$x+3$ [Son].
$9x+3$ [Father].

$\Rightarrow 6(x+3)=9x+3$
$\therefore x=5$

So, Son's age is 5 years.

Let: $f$ be the Fathers age and $s$ be the sons age

From the question we can gather that:

$f = 9s,~ f + 3 = 6(s + 3)$

Substitute the $f$ in the second equation with the $f$ in the first equation

$(9s) + 3 = 6(s + 3)$

Then rearrange to find $s$

$9s + 3 = 6s + 18$

$3s + 3 = 18$

$3s = 15$

$\large \boxed{s = 5}$