-38.1% is the change from 840 to 520
Calculation steps:
[( 520 - 840 ) ÷ 840] x 100 = -38.1%
Formula
Percentage change = [(520 - 840) / 840] x 100
Subtract the new number by the original number
520 - 840 = -320
-320 ÷ 840 = -0.38095238095238093
-0.38095238095238093 x 100 = -38.1%