-21.65% is the change from 850 to 666
Calculation steps:
[( 666 - 850 ) ÷ 850] x 100 = -21.65%
Formula
Percentage change = [(666 - 850) / 850] x 100
Subtract the new number by the original number
666 - 850 = -184
-184 ÷ 850 = -0.2164705882352941
-0.2164705882352941 x 100 = -21.65%