-17.5% is the change from 280 to 231
Calculation steps:
[( 231 - 280 ) ÷ 280] x 100 = -17.5%
Formula
Percentage change = [(231 - 280) / 280] x 100
Subtract the new number by the original number
231 - 280 = -49
-49 ÷ 280 = -0.175
-0.175 x 100 = -17.5%