-21.42% is the change from 817 to 642
Calculation steps:
[( 642 - 817 ) ÷ 817] x 100 = -21.42%
Formula
Percentage change = [(642 - 817) / 817] x 100
Subtract the new number by the original number
642 - 817 = -175
-175 ÷ 817 = -0.2141982864137087
-0.2141982864137087 x 100 = -21.42%