-97.7% is the change from 521 to 12
Calculation steps:
[( 12 - 521 ) ÷ 521] x 100 = -97.7%
Formula
Percentage change = [(12 - 521) / 521] x 100
Subtract the new number by the original number
12 - 521 = -509
-509 ÷ 521 = -0.9769673704414588
-0.9769673704414588 x 100 = -97.7%