-90% is the change from 30 to 3
Calculation steps:
[( 3 - 30 ) ÷ 30] x 100 = -90%
Formula
Percentage change = [(3 - 30) / 30] x 100
Subtract the new number by the original number
3 - 30 = -27
-27 ÷ 30 = -0.9
-0.9 x 100 = -90%
Example