It occurred to us to ask a puzzle fan, how old he was. The answer was somewhat elaborate ...
Take three years the years I will have in three years and restore three times the years I was three years ago and you will have exactly the years I am now.
How old is the individual?
If we take X as the age of our friend we have to three times the age that he will be in three years can be expressed as 3 (X + 3) to which we must subtract three times the age he was three years ago, that is 3 (X - 3). This will give us the age of the individual in question. Thus the complete equation would be as follows:
3 (X + 3) - 3 (X - 3) = x
If we clear the X from the equation we will have that X = 18 so we know that our friend is 18 years old.