-86.36% is the change from 660 to 90
Calculation steps:
[( 90 - 660 ) ÷ 660] x 100 = -86.36%
Formula
Percentage change = [(90 - 660) / 660] x 100
Subtract the new number by the original number
90 - 660 = -570
-570 ÷ 660 = -0.8636363636363636
-0.8636363636363636 x 100 = -86.36%