7.69% is the change from 390 to 420
Calculation steps:
[( 420 - 390 ) ÷ 390] x 100 = 7.69%
Formula
Percentage change = [(420 - 390) / 390] x 100
Subtract the new number by the original number
420 - 390 = 30
30 ÷ 390 = 0.07692307692307693
0.07692307692307693 x 100 = 7.69%