a man is 24 but only has 6 birthdays?
That man was born on February 29, or in leap year. Leap year happens once every four years so if you do the math, 24 years old / 6 birthdays = 4 years per birthday. He has still lived for 24 years, it's just that his birth date is rarer than a year is. F is 7 times as old as A.