Question 1968
you need to define a starting point, so...

let x = son's age now

father is now 38. When his son was born (x years ago) his age was that of his son now (x). So, father was 38-x but this equal x

so 38-x=x
2x=38
x=19.

check this...son now 19 and father 38. 19 years ago, son was born and father would have been 19..so correct.

To answer the question then, 5 years ago, son was 14.



cheers
Jon