-80% is the change from 85 to 17
Calculation steps:
[( 17 - 85 ) ÷ 85] x 100 = -80%
Formula
Percentage change = [(17 - 85) / 85] x 100
Subtract the new number by the original number
17 - 85 = -68
-68 ÷ 85 = -0.8
-0.8 x 100 = -80%
Example