-2.78% is the change from 864 to 840
Calculation steps:
[( 840 - 864 ) ÷ 864] x 100 = -2.78%
Formula
Percentage change = [(840 - 864) / 864] x 100
Subtract the new number by the original number
840 - 864 = -24
-24 ÷ 864 = -0.027777777777777776
-0.027777777777777776 x 100 = -2.78%