-70% is the change from 40 to 12
Calculation steps:
[( 12 - 40 ) ÷ 40] x 100 = -70%
Formula
Percentage change = [(12 - 40) / 40] x 100
Subtract the new number by the original number
12 - 40 = -28
-28 ÷ 40 = -0.7
-0.7 x 100 = -70%
Example