-2.5% is the change from 280 to 273
Calculation steps:
[( 273 - 280 ) ÷ 280] x 100 = -2.5%
Formula
Percentage change = [(273 - 280) / 280] x 100
Subtract the new number by the original number
273 - 280 = -7
-7 ÷ 280 = -0.025
-0.025 x 100 = -2.5%
Example