-87.84% is the change from 666 to 81
Calculation steps:
[( 81 - 666 ) ÷ 666] x 100 = -87.84%
Formula
Percentage change = [(81 - 666) / 666] x 100
Subtract the new number by the original number
81 - 666 = -585
-585 ÷ 666 = -0.8783783783783784
-0.8783783783783784 x 100 = -87.84%