-97.53% is the change from 850 to 21
Calculation steps:
[( 21 - 850 ) ÷ 850] x 100 = -97.53%
Formula
Percentage change = [(21 - 850) / 850] x 100
Subtract the new number by the original number
21 - 850 = -829
-829 ÷ 850 = -0.9752941176470589
-0.9752941176470589 x 100 = -97.53%