Problems on Ages - General Questions

A father is 5 times as old as his son. After 3 years he will be 4 times as old as his son. What is the father's present age?

6 years ago, A was 4 times as old as B. A is now 24 years older than B. What is B's present age?

The ratio of the present ages of A and B is 4 : 5. After 9 years the ratio will be 7 : 8. What is A's present age?

The ratio of the present ages of A and B is 3 : 4. After 7 years the ratio will be 31 : 39. What is A's present age?

The sum of the ages of two brothers is 33 years and the elder is 15 years older than the younger. What is the age of the elder brother?