-8.7% is the change from 920 to 840
Calculation steps:
[( 840 - 920 ) ÷ 920] x 100 = -8.7%
Formula
Percentage change = [(840 - 920) / 920] x 100
Subtract the new number by the original number
840 - 920 = -80
-80 ÷ 920 = -0.08695652173913043
-0.08695652173913043 x 100 = -8.7%