-34% is the change from 100 to 66
Calculation steps:
[( 66 - 100 ) ÷ 100] x 100 = -34%
Formula
Percentage change = [(66 - 100) / 100] x 100
Subtract the new number by the original number
66 - 100 = -34
-34 ÷ 100 = -0.34
-0.34 x 100 = -34%
Example