30.9% is the change from 398 to 521
Calculation steps:
[( 521 - 398 ) ÷ 398] x 100 = 30.9%
Formula
Percentage change = [(521 - 398) / 398] x 100
Subtract the new number by the original number
521 - 398 = 123
123 ÷ 398 = 0.30904522613065327
0.30904522613065327 x 100 = 30.9%