-26.1% is the change from 866 to 640
Calculation steps:
[( 640 - 866 ) ÷ 866] x 100 = -26.1%
Formula
Percentage change = [(640 - 866) / 866] x 100
Subtract the new number by the original number
640 - 866 = -226
-226 ÷ 866 = -0.26096997690531176
-0.26096997690531176 x 100 = -26.1%