-20% is the change from 10 to 8
Calculation steps:
[( 8 - 10 ) ÷ 10] x 100 = -20%
Formula
Percentage change = [(8 - 10) / 10] x 100
Subtract the new number by the original number
8 - 10 = -2
-2 ÷ 10 = -0.2
-0.2 x 100 = -20%
Example