The father is 24 years old, and the son is 6 years old.
Let x represent the son's age.
Let y represent the man's age.
Make two equations:
(1) The man's age is equal to four times his son's age:
(2) In three years the man's age will be
In three years the son's age will be
In three years the man's age will be equal to three times his son's age.
Expand the second equation:
Equate the two equations:
Simplify the equation:
Substitute this value into the first equation:
Therefore the son's age