-20.71% is the change from 840 to 666
Calculation steps:
[( 666 - 840 ) ÷ 840] x 100 = -20.71%
Formula
Percentage change = [(666 - 840) / 840] x 100
Subtract the new number by the original number
666 - 840 = -174
-174 ÷ 840 = -0.20714285714285716
-0.20714285714285716 x 100 = -20.71%