-73.75% is the change from 80 to 21
Calculation steps:
[( 21 - 80 ) ÷ 80] x 100 = -73.75%
Formula
Percentage change = [(21 - 80) / 80] x 100
Subtract the new number by the original number
21 - 80 = -59
-59 ÷ 80 = -0.7375
-0.7375 x 100 = -73.75%
Example