-86.92% is the change from 390 to 51
Calculation steps:
[( 51 - 390 ) ÷ 390] x 100 = -86.92%
Formula
Percentage change = [(51 - 390) / 390] x 100
Subtract the new number by the original number
51 - 390 = -339
-339 ÷ 390 = -0.8692307692307693
-0.8692307692307693 x 100 = -86.92%