-39.72% is the change from 642 to 387
Calculation steps:
[( 387 - 642 ) ÷ 642] x 100 = -39.72%
Formula
Percentage change = [(387 - 642) / 642] x 100
Subtract the new number by the original number
387 - 642 = -255
-255 ÷ 642 = -0.397196261682243
-0.397196261682243 x 100 = -39.72%