-19.28% is the change from 830 to 670
Calculation steps:
[( 670 - 830 ) ÷ 830] x 100 = -19.28%
Formula
Percentage change = [(670 - 830) / 830] x 100
Subtract the new number by the original number
670 - 830 = -160
-160 ÷ 830 = -0.1927710843373494
-0.1927710843373494 x 100 = -19.28%