8.42% is the change from 285 to 309
Calculation steps:
[( 309 - 285 ) ÷ 285] x 100 = 8.42%
Formula
Percentage change = [(309 - 285) / 285] x 100
Subtract the new number by the original number
309 - 285 = 24
24 ÷ 285 = 0.08421052631578947
0.08421052631578947 x 100 = 8.42%