Anon gets a new Step Mommy

Let x = how old anon is.
If anon is fifteen years older than the girlfriend, then it would be x + 15. We don't have any other data, so anon is x + 15 years old.

By my calculations OP has to be at least 33 years old for the relation to be legal, and 45 for the relation not to be creepy

Wait, x=anon=x+15???