-2.78% is the change from 324 to 315
Calculation steps:
[( 315 - 324 ) ÷ 324] x 100 = -2.78%
Formula
Percentage change = [(315 - 324) / 324] x 100
Subtract the new number by the original number
315 - 324 = -9
-9 ÷ 324 = -0.027777777777777776
-0.027777777777777776 x 100 = -2.78%