97.8% is the change from 91 to 180
Calculation steps:
[( 180 - 91 ) ÷ 91] x 100 = 97.8%
Formula
Percentage change = [(180 - 91) / 91] x 100
Subtract the new number by the original number
180 - 91 = 89
89 ÷ 91 = 0.978021978021978
0.978021978021978 x 100 = 97.8%