Disgusting Demotion WTF RIOT?????

So I got like 15/8/15 and my team is total trash. 3 trash teams in a row and this is my first game at 0 points.

My last like 8 games I have high MMR all games except one I had A and S scores.

I GET AN "S" on Akali.

And i get demoted and drop to 75, I mean wtf... 75? i JUST GOT AN S AND WAS THE BEST ON BOTH TEAMS.

this is total trash riot wtf