-90.47% is the change from 850 to 81
Calculation steps:
[( 81 - 850 ) ÷ 850] x 100 = -90.47%
Formula
Percentage change = [(81 - 850) / 850] x 100
Subtract the new number by the original number
81 - 850 = -769
-769 ÷ 850 = -0.9047058823529411
-0.9047058823529411 x 100 = -90.47%