42.5% is the change from 280 to 399
Calculation steps:
[( 399 - 280 ) ÷ 280] x 100 = 42.5%
Formula
Percentage change = [(399 - 280) / 280] x 100
Subtract the new number by the original number
399 - 280 = 119
119 ÷ 280 = 0.425
0.425 x 100 = 42.5%
Example