3900% is the change from 2 to 80
Calculation steps:
[( 80 - 2 ) ÷ 2] x 100 = 3900%
Formula
Percentage change = [(80 - 2) / 2] x 100
Subtract the new number by the original number
80 - 2 = 78
78 ÷ 2 = 39
39 x 100 = 3900%
Example