-80% is the change from 680 to 136
Calculation steps:
[( 136 - 680 ) ÷ 680] x 100 = -80%
Formula
Percentage change = [(136 - 680) / 680] x 100
Subtract the new number by the original number
136 - 680 = -544
-544 ÷ 680 = -0.8
-0.8 x 100 = -80%
Example