-97.74% is the change from 665 to 15
Calculation steps:
[( 15 - 665 ) ÷ 665] x 100 = -97.74%
Formula
Percentage change = [(15 - 665) / 665] x 100
Subtract the new number by the original number
15 - 665 = -650
-650 ÷ 665 = -0.9774436090225563
-0.9774436090225563 x 100 = -97.74%