900% is the change from 80 to 800
Calculation steps:
[( 800 - 80 ) ÷ 80] x 100 = 900%
Formula
Percentage change = [(800 - 80) / 80] x 100
Subtract the new number by the original number
800 - 80 = 720
720 ÷ 80 = 9
9 x 100 = 900%
Example