-84.76% is the change from 840 to 128
Calculation steps:
[( 128 - 840 ) ÷ 840] x 100 = -84.76%
Formula
Percentage change = [(128 - 840) / 840] x 100
Subtract the new number by the original number
128 - 840 = -712
-712 ÷ 840 = -0.8476190476190476
-0.8476190476190476 x 100 = -84.76%