-40% is the change from 210 to 126
Calculation steps:
[( 126 - 210 ) ÷ 210] x 100 = -40%
Formula
Percentage change = [(126 - 210) / 210] x 100
Subtract the new number by the original number
126 - 210 = -84
-84 ÷ 210 = -0.4
-0.4 x 100 = -40%
Example