-66.87% is the change from 839 to 278
Calculation steps:
[( 278 - 839 ) ÷ 839] x 100 = -66.87%
Formula
Percentage change = [(278 - 839) / 839] x 100
Subtract the new number by the original number
278 - 839 = -561
-561 ÷ 839 = -0.6686531585220501
-0.6686531585220501 x 100 = -66.87%