-9.77% is the change from 921 to 831
Calculation steps:
[( 831 - 921 ) ÷ 921] x 100 = -9.77%
Formula
Percentage change = [(831 - 921) / 921] x 100
Subtract the new number by the original number
831 - 921 = -90
-90 ÷ 921 = -0.09771986970684039
-0.09771986970684039 x 100 = -9.77%