-89.29% is the change from 840 to 90
Calculation steps:
[( 90 - 840 ) ÷ 840] x 100 = -89.29%
Formula
Percentage change = [(90 - 840) / 840] x 100
Subtract the new number by the original number
90 - 840 = -750
-750 ÷ 840 = -0.8928571428571429
-0.8928571428571429 x 100 = -89.29%