-91.18% is the change from 170 to 15
Calculation steps:
[( 15 - 170 ) ÷ 170] x 100 = -91.18%
Formula
Percentage change = [(15 - 170) / 170] x 100
Subtract the new number by the original number
15 - 170 = -155
-155 ÷ 170 = -0.9117647058823529
-0.9117647058823529 x 100 = -91.18%