-97.62% is the change from 840 to 20
Calculation steps:
[( 20 - 840 ) ÷ 840] x 100 = -97.62%
Formula
Percentage change = [(20 - 840) / 840] x 100
Subtract the new number by the original number
20 - 840 = -820
-820 ÷ 840 = -0.9761904761904762
-0.9761904761904762 x 100 = -97.62%