-38.71% is the change from 850 to 521
Calculation steps:
[( 521 - 850 ) ÷ 850] x 100 = -38.71%
Formula
Percentage change = [(521 - 850) / 850] x 100
Subtract the new number by the original number
521 - 850 = -329
-329 ÷ 850 = -0.3870588235294118
-0.3870588235294118 x 100 = -38.71%