Too all people who did their provisionals last minute and was placed in gold

It depends on your previous season's ranking.

In general it's not really possible to predict placement based on number of wins alone. This is for a couple of reasons.

First, the system values the first few placement games above other ones. Two people who both go 8-2 may get fairly different placements if one of them lost his first two games and the other one lost his last two.

Second, your placement will depend on the mmr of the people you're playing against, which would normally be pretty similar for people just starting out in ranked but may be effected by duo queueing etc.

I'm confused how the system works then. Because in the first month of season 4 I go 8-2 get put in silver 4 and was in silver 5. 8 months later or so brother does them goes 6-4 gets silver 3. The system puts people pretty much in silver 3 regardless of what they do towards the end of the season from nearly every single friend I know. I have friends who just got level 30 did placements went 4-6 got silver 3 as well.

I went 2/8 and got put in Bronze 2 (^:

I'm confused how the system works then. Because in the first month of season 4 I go 8-2 get put in silver 4 and was in silver 5. 8 months later or so brother does them goes 6-4 gets silver 3. The system puts people pretty much in silver 3 regardless of what they do towards the end of the season from nearly every single friend I know. I have friends who just got level 30 did placements went 4-6 got silver 3 as well.

The system always has gone off of elo, or as they call it now, MMR (matchmaking rating). At the beginning of each new season, everyone will receive what's called a 'soft reset.' This means that we will all get set a little closer to 1200 elo/mmr. People in bronze are the only ones that go up, and the higher up the rest of us are, the more we're affected.

Now even if two people ended the season at gold 1 last season and both go 8-2 in their promos, they may not get placed into the same rank. One could get back in gold 1 or 2, and one could get gold 5. I can't pretend to understand the complex algorithms that go into the ratings, but there are a lot of factors that go into the process.

Another thing to note is that the rank that is shown on your profile does not always reflect your mmr or elo accurately. There are some people that have a much lower mmr than their rank, some that are about even, and some that are consistently playing against people above their rank (but their mmr is ~ equal to those people!).

In your case, I would guess that you ended last season in low silver/high bronze and your brother either had a higher mmr, duo'd in promos, or faced higher mmr opponents (which would be the case for your lv 30, which start at 1200mmr as unranked, friends also).