-83.88% is the change from 521 to 84
Calculation steps:
[( 84 - 521 ) ÷ 521] x 100 = -83.88%
Formula
Percentage change = [(84 - 521) / 521] x 100
Subtract the new number by the original number
84 - 521 = -437
-437 ÷ 521 = -0.8387715930902111
-0.8387715930902111 x 100 = -83.88%