-20.36% is the change from 840 to 669
Calculation steps:
[( 669 - 840 ) ÷ 840] x 100 = -20.36%
Formula
Percentage change = [(669 - 840) / 840] x 100
Subtract the new number by the original number
669 - 840 = -171
-171 ÷ 840 = -0.20357142857142857
-0.20357142857142857 x 100 = -20.36%