3150% is the change from 12 to 390
Calculation steps:
[( 390 - 12 ) ÷ 12] x 100 = 3150%
Formula
Percentage change = [(390 - 12) / 12] x 100
Subtract the new number by the original number
390 - 12 = 378
378 ÷ 12 = 31.5
31.5 x 100 = 3150%
Example