-34.38% is the change from 320 to 210
Calculation steps:
[( 210 - 320 ) ÷ 320] x 100 = -34.38%
Formula
Percentage change = [(210 - 320) / 320] x 100
Subtract the new number by the original number
210 - 320 = -110
-110 ÷ 320 = -0.34375
-0.34375 x 100 = -34.38%