24.3% is the change from 321 to 399
Calculation steps:
[( 399 - 321 ) ÷ 321] x 100 = 24.3%
Formula
Percentage change = [(399 - 321) / 321] x 100
Subtract the new number by the original number
399 - 321 = 78
78 ÷ 321 = 0.24299065420560748
0.24299065420560748 x 100 = 24.3%