-42.11% is the change from 900 to 521
Calculation steps:
[( 521 - 900 ) ÷ 900] x 100 = -42.11%
Formula
Percentage change = [(521 - 900) / 900] x 100
Subtract the new number by the original number
521 - 900 = -379
-379 ÷ 900 = -0.4211111111111111
-0.4211111111111111 x 100 = -42.11%