-35.48% is the change from 31 to 20
Calculation steps:
[( 20 - 31 ) ÷ 31] x 100 = -35.48%
Formula
Percentage change = [(20 - 31) / 31] x 100
Subtract the new number by the original number
20 - 31 = -11
-11 ÷ 31 = -0.3548387096774194
-0.3548387096774194 x 100 = -35.48%