In Soccer-Game we have three outputs, win / draw / loose, with corresponding quotes q1 / q0 / q2. Now suppose we would like to bet x to win and y to draw. We have two back quotes.
In Exchanges, there exists another option, to Lay. Betting of the opposite and taking the role of the bookmaker. Therefore there exists an equivalent lay-quote + back-quote, ie. Lay q2 with x* and back q1 or q0 with y*.
How to get x*, y*?