-97.5% is the change from 839 to 21
Calculation steps:
[( 21 - 839 ) ÷ 839] x 100 = -97.5%
Formula
Percentage change = [(21 - 839) / 839] x 100
Subtract the new number by the original number
21 - 839 = -818
-818 ÷ 839 = -0.9749702026221693
-0.9749702026221693 x 100 = -97.5%