Which MMR does Count

Hi all.

I just had some thoughts about my placement matches. Which MMR counts to determine how much LP/MMR I gain/lose. Is it my team's or mine. A hypothetical scenario: My MMR is 100 My DuoQ guy is on 50 My team is on 75 Their team is on 80 If I win this game, do I gain MMR/LP based on the 75 vs. 80 rating (good for me) or based on the 100 vs. 80 rating (terrible for me). Would be nice to know since it could have a big impact on my decision whether I should play with a friend who is ranked below me or not.

Thanks for your help!