-80% is the change from 170 to 34
Calculation steps:
[( 34 - 170 ) ÷ 170] x 100 = -80%
Formula
Percentage change = [(34 - 170) / 170] x 100
Subtract the new number by the original number
34 - 170 = -136
-136 ÷ 170 = -0.8
-0.8 x 100 = -80%
Example