-50% is the change from 26 to 13
Calculation steps:
[( 13 - 26 ) ÷ 26] x 100 = -50%
Formula
Percentage change = [(13 - 26) / 26] x 100
Subtract the new number by the original number
13 - 26 = -13
-13 ÷ 26 = -0.5
-0.5 x 100 = -50%
Example