-19.02% is the change from 815 to 660
Calculation steps:
[( 660 - 815 ) ÷ 815] x 100 = -19.02%
Formula
Percentage change = [(660 - 815) / 815] x 100
Subtract the new number by the original number
660 - 815 = -155
-155 ÷ 815 = -0.1901840490797546
-0.1901840490797546 x 100 = -19.02%