30.05% is the change from 639 to 831
Calculation steps:
[( 831 - 639 ) ÷ 639] x 100 = 30.05%
Formula
Percentage change = [(831 - 639) / 639] x 100
Subtract the new number by the original number
831 - 639 = 192
192 ÷ 639 = 0.3004694835680751
0.3004694835680751 x 100 = 30.05%