-77% is the change from 639 to 147
Calculation steps:
[( 147 - 639 ) ÷ 639] x 100 = -77%
Formula
Percentage change = [(147 - 639) / 639] x 100
Subtract the new number by the original number
147 - 639 = -492
-492 ÷ 639 = -0.7699530516431925
-0.7699530516431925 x 100 = -77%