-88.75% is the change from 80 to 9
Calculation steps:
[( 9 - 80 ) ÷ 80] x 100 = -88.75%
Formula
Percentage change = [(9 - 80) / 80] x 100
Subtract the new number by the original number
9 - 80 = -71
-71 ÷ 80 = -0.8875
-0.8875 x 100 = -88.75%
Example