1, because the age difference between father and son is unchanged, it can be assumed that the age difference between father and son is a.

2. According to "When I was your age, you were only 4 years old", A's father and son have age difference;

3. When the father is 79 years old, the father is over A and the son is over A. ..

4, that is, from the age of 4 to the age of 79, the difference between father and son is 3 years.

explain

79-4=75 years old

75/3=25 years old, which means that the difference between father and son is 25 years old.

25+4=29 years old My son is 29 years old this year.

29+25=54 years old My father is 54 years old this year.