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

Let the present age of the man be $M$ and the present age of the son be $S$.
1. Condition 1 (Six years hence):

$$M+6=3(S+6)$$

$$M+6=3S+18⟹M-3S=12\text{— (Equation 1)}$$

2. Condition 2 (Three years ago):

$$M-3=9(S-3)$$

$$M-3=9S-27⟹M-9S=-24\text{— (Equation 2)}$$

Subtract Equation 2 from Equation 1:

$$(M-3S)-(M-9S)=12-(-24)$$

$$6S=36⟹S=6$$

Substitute $S=6$ back into Equation 1:

$$M-3(6)=12$$

$$M-18=12⟹M=30$$

Thus, the present age of the man is $30$ years.