-98.64% is the change from 660 to 9
Calculation steps:
[( 9 - 660 ) ÷ 660] x 100 = -98.64%
Formula
Percentage change = [(9 - 660) / 660] x 100
Subtract the new number by the original number
9 - 660 = -651
-651 ÷ 660 = -0.9863636363636363
-0.9863636363636363 x 100 = -98.64%