-20.87% is the change from 115 to 91
Calculation steps:
[( 91 - 115 ) ÷ 115] x 100 = -20.87%
Formula
Percentage change = [(91 - 115) / 115] x 100
Subtract the new number by the original number
91 - 115 = -24
-24 ÷ 115 = -0.20869565217391303
-0.20869565217391303 x 100 = -20.87%