31.5% is the change from 638 to 839
Calculation steps:
[( 839 - 638 ) ÷ 638] x 100 = 31.5%
Formula
Percentage change = [(839 - 638) / 638] x 100
Subtract the new number by the original number
839 - 638 = 201
201 ÷ 638 = 0.31504702194357365
0.31504702194357365 x 100 = 31.5%