-90.11% is the change from 91 to 9
Calculation steps:
[( 9 - 91 ) ÷ 91] x 100 = -90.11%
Formula
Percentage change = [(9 - 91) / 91] x 100
Subtract the new number by the original number
9 - 91 = -82
-82 ÷ 91 = -0.9010989010989011
-0.9010989010989011 x 100 = -90.11%