Replacement games

Why do you think you should had been ranked lower? It's actually really hard to be placed in bronze. Also the early games count more than the later ones, so if the 3 you won were in the first half, the mmr you gained will be higher than the mmr you lost losing games in the second half.

At the start of season 6 i lost all my placement games and ended in silver 5 and was only silver 1 the previous seaso (now i'm gold 1). My friend won all his games and was still placed in bronze. Its about who you were facing (their elo) and what your previous elo was as well as some in game factors. I don't think riot really cares about placements since they are just a starting point and anyone can climb up after or fall where they belong later on. Its just to gauge whether you should start at an elo/division and what would be best for your experience to be started at.

Also look at your mmr using op.gg usually mmr is good indicator whether you actually currently belong at that elo and is usually used behind the scenes. It determines the rank of the other players that you are gonna be matched against in your placement games.

Here is your link for op.gg in case you are unfamiliar with the site: http://eune.op.gg/summoner/userName=madalaki12

PS use op.gg it can really help and you can also use champion.gg to see good builds and what to do not each champs as well as their current winrate.