-30.74% is the change from 924 to 640
Calculation steps:
[( 640 - 924 ) ÷ 924] x 100 = -30.74%
Formula
Percentage change = [(640 - 924) / 924] x 100
Subtract the new number by the original number
640 - 924 = -284
-284 ÷ 924 = -0.30735930735930733
-0.30735930735930733 x 100 = -30.74%