-81.33% is the change from 830 to 155
Calculation steps:
[( 155 - 830 ) ÷ 830] x 100 = -81.33%
Formula
Percentage change = [(155 - 830) / 830] x 100
Subtract the new number by the original number
155 - 830 = -675
-675 ÷ 830 = -0.8132530120481928
-0.8132530120481928 x 100 = -81.33%