A man is 6 time old then his son 20 years later the man will be twice as old as his son find the age of man when his son was born

Let's assume the current age of the son is x.

According to the statement, the current age of the man is 6 times the age of the son, so the man's current age is 6x.
20 years later, the son's age will be x + 20, and the man's age will be 6x + 20.
According to the second part of the statement, 20 years later, the man will be twice as old as his son. So, we have the equation:
6x + 20 = 2(x + 20)
6x + 20 = 2x + 40
6x - 2x = 40 - 20
4x = 20
x = 5
Therefore, the current age of the son is 5.
The age of the man when his son was born is given by:
6x - x = 5(6) - 5(1) = 30 - 5 = <<30-5=25>>25 years old. Answer: \boxed{25}.

Let's solve this step-by-step.

Let's assume the current age of the son is "x".

According to the given information, the man is 6 times older than his son. So, the current age of the man would be 6x.

After 20 years, the age of the son would be x + 20, and the age of the man would be 6x + 20.

It is also given that 20 years later, the man would be twice as old as his son.

So, we can form the following equation: (6x + 20) = 2(x + 20)

Now, let's solve this equation step-by-step:

6x + 20 = 2x + 40 [Distributed the 2 on the right side]

6x - 2x + 20 = 40 [Subtracted 2x from both sides]

4x + 20 = 40 [Simplified]

4x = 40 - 20 [Subtracted 20 from both sides]

4x = 20 [Simplified]

Dividing both sides of the equation by 4:

4x/4 = 20/4

x = 5

Therefore, the current age of the son is 5 years.

To find the age of the man when his son was born, we need to subtract the son's age from the current age of the man.

Current age of the man = 6x = 6 * 5 = 30

Age of the man when his son was born = current age of the man - son's current age

= 30 - 5

= 25

So, the age of the man when his son was born is 25 years.