13.75% is the change from 80 to 91
Calculation steps:
[( 91 - 80 ) ÷ 80] x 100 = 13.75%
Formula
Percentage change = [(91 - 80) / 80] x 100
Subtract the new number by the original number
91 - 80 = 11
11 ÷ 80 = 0.1375
0.1375 x 100 = 13.75%
Example