We start by defining Archie's age which we don't know at the moment, so we'll just represent it with the symbol 'x'.
Then, we're told that his son's age is 5 more than one-quarter (1/4) of Archie's age.
In mathematics, the phrase "more than" often translates to an addition operation. So, to get the son's age, we will first need to take one-fourth of Archie's age, and then add 5 to that.
This gives us the following algebraic expression for the son's age:
1/4 * Archie's age (which is 'x') + 5
So, we can therefore express the son's age as:
0.25*x + 5