-60% is the change from 320 to 128
Calculation steps:
[( 128 - 320 ) ÷ 320] x 100 = -60%
Formula
Percentage change = [(128 - 320) / 320] x 100
Subtract the new number by the original number
128 - 320 = -192
-192 ÷ 320 = -0.6
-0.6 x 100 = -60%
Example