Something about sure wins

The newest and most modern way of betting is the sure win method. It is based to a competition between bookmakers and to a differences of odds that they give. Mostly this difference is not so high to erase the margin of bookmakers, but sometimes iot works.
First we should explain how the odds are calculated by bookmakers. Thgey first decide what they expect from the match. So if the match is Liverpool - Manchester United, the bookmakers decide that the odds are: Liverpool wins 30%, Draw 40% and Manchester wins 30%. So to make the coeficients bookmakers devide 1 to the percentage that is given. This means that if you realize a bet to every coeficient you will not lose a cent.
This is not true in the real game. Every bookmaker make a margin. The margin is mostly 10% (or more). This is the winning of bookmaker. He don't care what is the end of the match. He has his profit.
Some bookmakers have different ideas about end of the match. For the same match another bookmaker may calculate the odds about Liverpool - Manchester United in the other way, just like: Liverpool wins 50%, Draw 30% and Manchester wins 20%. The third bookmaker may give 50% for a winning of Manchester. So that is the idea of sure win. You will bet for different bookmakers for every sign.