-51.25% is the change from 800 to 390
Calculation steps:
[( 390 - 800 ) ÷ 800] x 100 = -51.25%
Formula
Percentage change = [(390 - 800) / 800] x 100
Subtract the new number by the original number
390 - 800 = -410
-410 ÷ 800 = -0.5125
-0.5125 x 100 = -51.25%