-67.5% is the change from 280 to 91
Calculation steps:
[( 91 - 280 ) ÷ 280] x 100 = -67.5%
Formula
Percentage change = [(91 - 280) / 280] x 100
Subtract the new number by the original number
91 - 280 = -189
-189 ÷ 280 = -0.675
-0.675 x 100 = -67.5%
Example