-90.8% is the change from 870 to 80
Calculation steps:
[( 80 - 870 ) ÷ 870] x 100 = -90.8%
Formula
Percentage change = [(80 - 870) / 870] x 100
Subtract the new number by the original number
80 - 870 = -790
-790 ÷ 870 = -0.9080459770114943
-0.9080459770114943 x 100 = -90.8%