-97.76% is the change from 670 to 15
Calculation steps:
[( 15 - 670 ) ÷ 670] x 100 = -97.76%
Formula
Percentage change = [(15 - 670) / 670] x 100
Subtract the new number by the original number
15 - 670 = -655
-655 ÷ 670 = -0.9776119402985075
-0.9776119402985075 x 100 = -97.76%