-2.73% is the change from 660 to 642
Calculation steps:
[( 642 - 660 ) ÷ 660] x 100 = -2.73%
Formula
Percentage change = [(642 - 660) / 660] x 100
Subtract the new number by the original number
642 - 660 = -18
-18 ÷ 660 = -0.02727272727272727
-0.02727272727272727 x 100 = -2.73%