-86.88% is the change from 320 to 42
Calculation steps:
[( 42 - 320 ) ÷ 320] x 100 = -86.88%
Formula
Percentage change = [(42 - 320) / 320] x 100
Subtract the new number by the original number
42 - 320 = -278
-278 ÷ 320 = -0.86875
-0.86875 x 100 = -86.88%