Expert: Scott A Wilson - 4/7/2011

Question
a man is six times as old as his son.in 7 1/2 years, he will be just three times as old as his son will be then . how old is the man?

Answer
Since 7.5 is mentioned, that must mean age is being looked at as having a half in it.

Let the father be F years old and his son be S years old.  
The 1st equation is F = 6S.
The 2nd equation is (F+7.5) = 3(S+7.5).

Multiplying the 2nd equation out gives F + 7.5 = 3S + 22.5.
Subtracting 7.5 from both sides gives F = 3S + 15.

Since we have F = 6S and F = 3S + 15, it can be said that 6S = 3S + 15.
Subtracting 3S from both sides gives 3S = 15, and dividing both sides by 3 gives S = 5.
Since that dad is six times as old, F = 6*5 = 30.

This means that the son was born when the dad was 25, and that was a good age to become a father.
If all things were done right and the dad was more than 3 months from his 26th birthday,
he must have been married when he was 24.