-87.69% is the change from 642 to 79
Calculation steps:
[( 79 - 642 ) ÷ 642] x 100 = -87.69%
Formula
Percentage change = [(79 - 642) / 642] x 100
Subtract the new number by the original number
79 - 642 = -563
-563 ÷ 642 = -0.8769470404984424
-0.8769470404984424 x 100 = -87.69%