If a father is 20 years older than his son. What is the sum of their age seven years ago? Hints: Let the son's age be x and the father's age be x + 20.

Seven years ago, the son's age would have been x - 7 and the father's age would have been (x + 20) - 7 = x + 13.

The sum of their ages seven years ago would be (x - 7) + (x + 13) = 2x + 6.

However, we don't know the current ages of the son and the father, so we can't solve for 2x + 6.

To solve this problem, we need to determine the sum of their ages seven years ago.

Let's assume the son's age is x years.

According to the given information, the father's age is 20 years older than the son's age, which means the father's age is (x + 20) years.

To find the sum of their ages seven years ago, we need to subtract seven from their current ages.

The son's age seven years ago would be (x - 7) years.

Similarly, the father's age seven years ago would be ((x + 20) - 7) years, which simplifies to (x + 13) years.

Now, we can calculate the sum of their ages seven years ago:

(x - 7) + (x + 13) = 2x + 6

Therefore, the sum of their ages seven years ago is 2x + 6.