-87.6% is the change from 645 to 80
Calculation steps:
[( 80 - 645 ) ÷ 645] x 100 = -87.6%
Formula
Percentage change = [(80 - 645) / 645] x 100
Subtract the new number by the original number
80 - 645 = -565
-565 ÷ 645 = -0.875968992248062
-0.875968992248062 x 100 = -87.6%