-87.65% is the change from 170 to 21
Calculation steps:
[( 21 - 170 ) ÷ 170] x 100 = -87.65%
Formula
Percentage change = [(21 - 170) / 170] x 100
Subtract the new number by the original number
21 - 170 = -149
-149 ÷ 170 = -0.8764705882352941
-0.8764705882352941 x 100 = -87.65%