I hope I get this right...
h = head length = 9
b = body length = 9 + t
t = tail length = 9 + 1/2b
We need to solve for the body or tail length: solve(b=9+t,t=9+1/2b) = {b=36, t=27}
I don't know what's wrong with 72 as an answer, CPhill. Or were you just making another pun?