A man was 32 years of age when he had his first son. His wife was 35 years of age when his son attained the age of 7 years. The difference between the age of the father and the mother is ______.

The age of father when his son attained the age of 7 years = 32 + 7 = 39 years
∴ Required difference = The age of father when his son attained the age of 7 years - The age of mother when her son attained the age of 7 years
The difference between the ages of father and mother = (39 – 35) years = 4 years