Not including four play in games, there are 64 teams in the tournament. once a team loses one game they are eliminated. how many games would have been played if each team had to play every other team once?

Every time teams play with each other (assuming there are no draws) half of them win
and the others get eliminated so
64÷2=32 32 games played and 32 teams eliminated
32÷2=16 16 games played and 16 teams eliminated
16÷2=8 the same goes here
8÷2=4 and here
4÷2=2 .
2÷2=1 .

32+16+8+4+2+1=63 games

Yes the slope to this is -5