-80% is the change from 210 to 42
Calculation steps:
[( 42 - 210 ) ÷ 210] x 100 = -80%
Formula
Percentage change = [(42 - 210) / 210] x 100
Subtract the new number by the original number
42 - 210 = -168
-168 ÷ 210 = -0.8
-0.8 x 100 = -80%
Example