How the ranked system works

Iam gold 5 and everytime I go adc its kinda easy. But there is always one troller or afkers that makes this game super sad to play. After the game when I check their matchhistory there are only loses. I don't understands how ppl like these come with me. And for somehow iam always lastpick. Riot really needs to improve their ranked system.
Report as:
Offensive Spam Harassment Incorrect Board