Given that the age of the son is 15 years old and the age of the father is three times the age of the son, we can calculate the age of the father using the equation:
Age of Father = 3 * Age of Son
Substitute the value of the son's age:
Age of Father = 3 * 15
Age of Father = 45 years
So, the age of the father is 45 years. None of the provided options (a, b, c, d) match the correct answer.