-50% is the change from 204 to 102
Calculation steps:
[( 102 - 204 ) ÷ 204] x 100 = -50%
Formula
Percentage change = [(102 - 204) / 204] x 100
Subtract the new number by the original number
102 - 204 = -102
-102 ÷ 204 = -0.5
-0.5 x 100 = -50%
Example