Question about Provisionals

I was wondering how the solo que provisional placements work. I notice some summoners in a local group are able to go 1/9 and be placed in Gold, others 4/6 and be placed Platinum. I myself was able to pull a score of 3/7 and was placed in bronze, where as last season i went 4/6 and was placed in silver. As this does upset me (as I never wanted to be in Bronze because of the community hate the division receives) I would first like to know how the placements work. I started about 7 or so months ago and I am not completely sure of the system yet. I look forward to the Replies of Riot Games staff to my inquiry. ~Cordel8a11 R.I.P. DFG