Placement Matches

The current placements are based off of MMR (match making rating) and I think this rating has to have some changes. First and foremost, I placed bronze V in both ranked solo/duo and ranked flex. I played support in every single one of those games and got an average score of A- in my ranked solo/duo games. I actually played well in 80% of the games, but in every game I lost there was a player who hard fed and f***ed the team over. Why should my MMR decrease because of the performance of other players?

Someone once told me that it was impossible to place well in bronze elo because of all the trolls. I don't see these people as trolls, they just play poorly - it happens to everyone. It's your rank, it should be based off you performance.

Is there a place that explains how your MMR and score after each game is calculated?