-50% is the change from 668 to 334
Calculation steps:
[( 334 - 668 ) ÷ 668] x 100 = -50%
Formula
Percentage change = [(334 - 668) / 668] x 100
Subtract the new number by the original number
334 - 668 = -334
-334 ÷ 668 = -0.5
-0.5 x 100 = -50%
Example