-50% is the change from 136 to 68
Calculation steps:
[( 68 - 136 ) ÷ 136] x 100 = -50%
Formula
Percentage change = [(68 - 136) / 136] x 100
Subtract the new number by the original number
68 - 136 = -68
-68 ÷ 136 = -0.5
-0.5 x 100 = -50%
Example