P = percent change
N = new value = 8
S = starting value = 15
P = 100*(N-S)/S
P = 100*(8-15)/15
P = 100*(-7)/15
P = -700/15
P = -46.67% approximately
So if they won 15 games last year, then 8 games this year, then the percent change is approximately -46.67%
The negative percent indicates "a drop" or "decrease" in value. So you could say "the number of games won dropped by roughly 46.67 percent"
