-3.7% is the change from 810 to 780
Calculation steps:
[( 780 - 810 ) ÷ 810] x 100 = -3.7%
Formula
Percentage change = [(780 - 810) / 810] x 100
Subtract the new number by the original number
780 - 810 = -30
-30 ÷ 810 = -0.037037037037037035
-0.037037037037037035 x 100 = -3.7%