Their Birthday

It's their birthday, you see,
The same for all three,
It's strange but it's perfectly true.

There's Bertie and Ben
Who differ by ten;
Eight years older than one there is Sue.

Double one brother,
Plus treble the other,
Plus Sue's age makes seventy-two.

From what's on this page
You can find the girl's age.
It's really quite easy to do.

(Hunter, J.A.H., (1956). Fun with Figures. New York: Dover Publishers, Inc.)