To solve the problem, let's first establish some mathematical equations based on the information given:

1. Let the current age of the son be x years.
2. Thus, the current age of the father would be f years.

The problem provides the following condition from the past:

• 3 years ago, the father's age was 24 years more than twice the son's age.

This can be translated into the equation:

(f - 3) = 2(x - 3) + 24

Simplifying this equation:

1. Distribute and simplify: f - 3 = 2x - 6 + 24
2. Combine like terms: f - 3 = 2x + 18
3. Rearrange to express in terms of f: f = 2x + 21

Now, the second condition asks us to find out after how many years will the father's age be twice his son's age:

• Let this number of years be n.
• We then form the future condition: (f + n) = 2(x + n)

Using the derived equation of the father's age, substitute f:

(2x + 21 + n) = 2(x + n)

Expanding and simplifying:

1. 2x + 21 + n = 2x + 2n
2. Subtract 2x from each side: 21 + n = 2n
3. Simplify to find n: 21 = n

Therefore, after 21 years, the father's age will be twice his son's age. Hence, the correct answer is:

Answer: 21