How is it possible to rank up?

I get 3lp for a win and 15 for a loss. How can I rank up?

This seems so unfair, I have 350 games in silver and get shit talked every game I play because of it. I have been trapped here for a long time. I get up to 90 lp in silver one, then lose two or three games and it takes me a week to get back to 90. How the fuck am I suppose to rank up like this? I basically need 20 or 30 wins a row.