30.67% is the change from 639 to 835
Calculation steps:
[( 835 - 639 ) ÷ 639] x 100 = 30.67%
Formula
Percentage change = [(835 - 639) / 639] x 100
Subtract the new number by the original number
835 - 639 = 196
196 ÷ 639 = 0.30672926447574334
0.30672926447574334 x 100 = 30.67%