Match Making Unbalance for solo que

Decided to go solo que and I ended up going against 4 diamond players and a plat... and my team (me) plat, another plat, a diamond, a gold and an unrank...? how does and unrank person get que up with us... also if the diamond and the unrank person was duo or triple or whatever how did we end up with 3 premade or 4 premade diamond players/plat person?????????????????????????????????????????????