-90.25% is the change from 831 to 81
Calculation steps:
[( 81 - 831 ) ÷ 831] x 100 = -90.25%
Formula
Percentage change = [(81 - 831) / 831] x 100
Subtract the new number by the original number
81 - 831 = -750
-750 ÷ 831 = -0.9025270758122743
-0.9025270758122743 x 100 = -90.25%