-87% is the change from 100 to 13
Calculation steps:
[( 13 - 100 ) ÷ 100] x 100 = -87%
Formula
Percentage change = [(13 - 100) / 100] x 100
Subtract the new number by the original number
13 - 100 = -87
-87 ÷ 100 = -0.87
-0.87 x 100 = -87%
Example