-8.59% is the change from 640 to 585
Calculation steps:
[( 585 - 640 ) ÷ 640] x 100 = -8.59%
Formula
Percentage change = [(585 - 640) / 640] x 100
Subtract the new number by the original number
585 - 640 = -55
-55 ÷ 640 = -0.0859375
-0.0859375 x 100 = -8.59%