-36.25% is the change from 80 to 51
Calculation steps:
[( 51 - 80 ) ÷ 80] x 100 = -36.25%
Formula
Percentage change = [(51 - 80) / 80] x 100
Subtract the new number by the original number
51 - 80 = -29
-29 ÷ 80 = -0.3625
-0.3625 x 100 = -36.25%
Example