-82.35% is the change from 85 to 15
Calculation steps:
[( 15 - 85 ) ÷ 85] x 100 = -82.35%
Formula
Percentage change = [(15 - 85) / 85] x 100
Subtract the new number by the original number
15 - 85 = -70
-70 ÷ 85 = -0.8235294117647058
-0.8235294117647058 x 100 = -82.35%