Six years hence a man's age will be three times the age of his son and three years ago he was nine times as old as his son. The present age of the man is

Present age of man $=x$

Age of             Son             $=y$

After 6 years, age of man$=x+6$

                        Age of son $=y+6$

Given $x+6=3\left(y+6\right)$

            $x-3y-12=0$ ………. (1)

Three years ago

            Age of man $=x-3$

             Age of son $=y-3$     

            Given $x-3=9\left(y-3\right)$

            $x-9y+24=0$  ……… (2)

Solve (1) and (2) we get $x=30,y=6$

$\therefore$          The age of man $=30$  years