-98.65% is the change from 666 to 9
Calculation steps:
[( 9 - 666 ) ÷ 666] x 100 = -98.65%
Formula
Percentage change = [(9 - 666) / 666] x 100
Subtract the new number by the original number
9 - 666 = -657
-657 ÷ 666 = -0.9864864864864865
-0.9864864864864865 x 100 = -98.65%