How does mmr work

so ive been playing valorant for a while now being on and off the game, i just came back and havent played in a act but when i play, i play with my boy and i top frag 8/10 times in general, in this one game for example i went 20/9/3 and he went 14/10 and got 36 rr perfermance boost 7, i got 28 rr, their have been multiple games like this.