-84.2% is the change from 500 to 79
Calculation steps:
[( 79 - 500 ) ÷ 500] x 100 = -84.2%
Formula
Percentage change = [(79 - 500) / 500] x 100
Subtract the new number by the original number
79 - 500 = -421
-421 ÷ 500 = -0.842
-0.842 x 100 = -84.2%
Example