-9.2% is the change from 870 to 790
Calculation steps:
[( 790 - 870 ) ÷ 870] x 100 = -9.2%
Formula
Percentage change = [(790 - 870) / 870] x 100
Subtract the new number by the original number
790 - 870 = -80
-80 ÷ 870 = -0.09195402298850575
-0.09195402298850575 x 100 = -9.2%