-47.5% is the change from 80 to 42
Calculation steps:
[( 42 - 80 ) ÷ 80] x 100 = -47.5%
Formula
Percentage change = [(42 - 80) / 80] x 100
Subtract the new number by the original number
42 - 80 = -38
-38 ÷ 80 = -0.475
-0.475 x 100 = -47.5%
Example