-3.9% is the change from 820 to 788
Calculation steps:
[( 788 - 820 ) ÷ 820] x 100 = -3.9%
Formula
Percentage change = [(788 - 820) / 820] x 100
Subtract the new number by the original number
788 - 820 = -32
-32 ÷ 820 = -0.03902439024390244
-0.03902439024390244 x 100 = -3.9%