-85.56% is the change from 90 to 13
Calculation steps:
[( 13 - 90 ) ÷ 90] x 100 = -85.56%
Formula
Percentage change = [(13 - 90) / 90] x 100
Subtract the new number by the original number
13 - 90 = -77
-77 ÷ 90 = -0.8555555555555555
-0.8555555555555555 x 100 = -85.56%