Hi guy's & doll's

I have excel 2007 with windows vista premium.am also quite new to excel.

Ive been trying to calculate some odds by hand i thought i got it but tried
some
different odds for hours now and am stuck.

Heres the situation team A has odds at 3.05 and team B at 5.10 odds.

So i totalled the two odds which came up as 8.15 then i subtracted 1 which
left 7.15.

After this i thought oh would it be nice to win £11.00 no matter what team
won.

I then divided £11.00 into 7.15 which gave 1.54 to two decimal places then i
simply
times this with the odds £4.69 at 5.10 and £7.85 at 3.05 which gave a profit
of £11.38 and £11.39 respectively.

This is when you take off the stake lets say team A won so it would be
£7.85 stake back plus minus the other lost of £4.69 leaving a profit of
£11.39.

But ive tried with different odds and it wont tally going over many
different things.

Can someone please help is there a formula for this or am i just wasting my
time.

May i take this opportunity to thank everyone in advance for your much
appreciated
help and time with my enquiry.

Paul.