-11.49% is the change from 870 to 770
Calculation steps:
[( 770 - 870 ) ÷ 870] x 100 = -11.49%
Formula
Percentage change = [(770 - 870) / 870] x 100
Subtract the new number by the original number
770 - 870 = -100
-100 ÷ 870 = -0.11494252873563218
-0.11494252873563218 x 100 = -11.49%