-19.82% is the change from 797 to 639
Calculation steps:
[( 639 - 797 ) ÷ 797] x 100 = -19.82%
Formula
Percentage change = [(639 - 797) / 797] x 100
Subtract the new number by the original number
639 - 797 = -158
-158 ÷ 797 = -0.19824341279799249
-0.19824341279799249 x 100 = -19.82%