-9.06% is the change from 320 to 291
Calculation steps:
[( 291 - 320 ) ÷ 320] x 100 = -9.06%
Formula
Percentage change = [(291 - 320) / 320] x 100
Subtract the new number by the original number
291 - 320 = -29
-29 ÷ 320 = -0.090625
-0.090625 x 100 = -9.06%