-17.17% is the change from 990 to 820
Calculation steps:
[( 820 - 990 ) ÷ 990] x 100 = -17.17%
Formula
Percentage change = [(820 - 990) / 990] x 100
Subtract the new number by the original number
820 - 990 = -170
-170 ÷ 990 = -0.1717171717171717
-0.1717171717171717 x 100 = -17.17%