-9.38% is the change from 320 to 290
Calculation steps:
[( 290 - 320 ) ÷ 320] x 100 = -9.38%
Formula
Percentage change = [(290 - 320) / 320] x 100
Subtract the new number by the original number
290 - 320 = -30
-30 ÷ 320 = -0.09375
-0.09375 x 100 = -9.38%