-8.75% is the change from 640 to 584
Calculation steps:
[( 584 - 640 ) ÷ 640] x 100 = -8.75%
Formula
Percentage change = [(584 - 640) / 640] x 100
Subtract the new number by the original number
584 - 640 = -56
-56 ÷ 640 = -0.0875
-0.0875 x 100 = -8.75%