Question 291249
Let M be the man's age, S be the son's.
Right now,
1.{{{M=9S}}}
In 9 years, the man will be M+9 and his son will be S+9.
2.{{{M+9=3(S+9)}}}
Substitute for M in eq. 2 using eq. 1 and solve for S.
{{{M+9=3(S+9)}}}
{{{9S+9=3S+27}}}
{{{6S=18}}}
{{{S=3}}}
Now go back to eq. 1,
{{{M=9S}}}
{{{M=9(3)}}}
{{{M=27}}}
Today, the man is 27 years old and his son is 3 years old.