Fraid I'm not a maths man.
(
Christian's Bolt and Ski,
Sat 20 Nov 2010, 18:05,
archived)
must be subtraction
(
LS18,
Sat 20 Nov 2010, 18:23,
archived)
It's an exclusive club
Either of you can be in, but not both.
(
RedHouse over yonder,
Sat 20 Nov 2010, 18:41,
archived)