The average age of father and his two sons is 27 Y ears. Five years ago, the average age of the two sons was 12 Y ears. If the difference between the ages of the two sons is four years, what is the present age of the father?

Solution: 
 The total present age of father and two sons is 3S27 = 81 yrs
The total present age of sons is (12+5) X 2 = 34 Yrs
so, present age of father is 81 - 34 = 47 yrs