-32.81% is the change from 320 to 215
Calculation steps:
[( 215 - 320 ) ÷ 320] x 100 = -32.81%
Formula
Percentage change = [(215 - 320) / 320] x 100
Subtract the new number by the original number
215 - 320 = -105
-105 ÷ 320 = -0.328125
-0.328125 x 100 = -32.81%