-21.65% is the change from 665 to 521
Calculation steps:
[( 521 - 665 ) ÷ 665] x 100 = -21.65%
Formula
Percentage change = [(521 - 665) / 665] x 100
Subtract the new number by the original number
521 - 665 = -144
-144 ÷ 665 = -0.21654135338345865
-0.21654135338345865 x 100 = -21.65%