-90.35% is the change from 839 to 81
Calculation steps:
[( 81 - 839 ) ÷ 839] x 100 = -90.35%
Formula
Percentage change = [(81 - 839) / 839] x 100
Subtract the new number by the original number
81 - 839 = -758
-758 ÷ 839 = -0.9034564958283671
-0.9034564958283671 x 100 = -90.35%