-17.19% is the change from 640 to 530
Calculation steps:
[( 530 - 640 ) ÷ 640] x 100 = -17.19%
Formula
Percentage change = [(530 - 640) / 640] x 100
Subtract the new number by the original number
530 - 640 = -110
-110 ÷ 640 = -0.171875
-0.171875 x 100 = -17.19%