25% is the change from 80 to 100
Calculation steps:
[( 100 - 80 ) ÷ 80] x 100 = 25%
Formula
Percentage change = [(100 - 80) / 80] x 100
Subtract the new number by the original number
100 - 80 = 20
20 ÷ 80 = 0.25
0.25 x 100 = 25%
Example