if you work with probability it might be a good idea if you think
about it as a tree (often it is a binary tree)

                                        A A vs. B            0.4   /                           \  0.6                        lost                            won A vs. C        0.4 /        \ 0.6              0.4 /        \ 0.6               lost             won              lost          won A vs. D      0.4 / \ 0.6   0.4 / \ 0.6      0.4 / \ 0.6    0.4 / \ 0.6               lost  won     lost  won       lost   won      lost   won

Now you search for the paths that you need. If A has to win all 3 Games only the right path fits. If you go down the tree you have to multiply the probabilities.

If more than one Path fits you need to search all the paths that get you the right result. Then you calculate the Probability for each of this paths and sum those probabilities up.