3.1% is the change from 840 to 866
Calculation steps:
[( 866 - 840 ) ÷ 840] x 100 = 3.1%
Formula
Percentage change = [(866 - 840) / 840] x 100
Subtract the new number by the original number
866 - 840 = 26
26 ÷ 840 = 0.030952380952380953
0.030952380952380953 x 100 = 3.1%