-80% is the change from 390 to 78
Calculation steps:
[( 78 - 390 ) ÷ 390] x 100 = -80%
Formula
Percentage change = [(78 - 390) / 390] x 100
Subtract the new number by the original number
78 - 390 = -312
-312 ÷ 390 = -0.8
-0.8 x 100 = -80%
Example