-80.31% is the change from 640 to 126
Calculation steps:
[( 126 - 640 ) ÷ 640] x 100 = -80.31%
Formula
Percentage change = [(126 - 640) / 640] x 100
Subtract the new number by the original number
126 - 640 = -514
-514 ÷ 640 = -0.803125
-0.803125 x 100 = -80.31%