-30.29% is the change from 921 to 642
Calculation steps:
[( 642 - 921 ) ÷ 921] x 100 = -30.29%
Formula
Percentage change = [(642 - 921) / 921] x 100
Subtract the new number by the original number
642 - 921 = -279
-279 ÷ 921 = -0.30293159609120524
-0.30293159609120524 x 100 = -30.29%