-80.47% is the change from 850 to 166
Calculation steps:
[( 166 - 850 ) ÷ 850] x 100 = -80.47%
Formula
Percentage change = [(166 - 850) / 850] x 100
Subtract the new number by the original number
166 - 850 = -684
-684 ÷ 850 = -0.8047058823529412
-0.8047058823529412 x 100 = -80.47%