-8.05% is the change from 870 to 800
Calculation steps:
[( 800 - 870 ) ÷ 870] x 100 = -8.05%
Formula
Percentage change = [(800 - 870) / 870] x 100
Subtract the new number by the original number
800 - 870 = -70
-70 ÷ 870 = -0.08045977011494253
-0.08045977011494253 x 100 = -8.05%