-62.5% is the change from 80 to 30
Calculation steps:
[( 30 - 80 ) ÷ 80] x 100 = -62.5%
Formula
Percentage change = [(30 - 80) / 80] x 100
Subtract the new number by the original number
30 - 80 = -50
-50 ÷ 80 = -0.625
-0.625 x 100 = -62.5%
Example