-66.39% is the change from 830 to 279
Calculation steps:
[( 279 - 830 ) ÷ 830] x 100 = -66.39%
Formula
Percentage change = [(279 - 830) / 830] x 100
Subtract the new number by the original number
279 - 830 = -551
-551 ÷ 830 = -0.6638554216867469
-0.6638554216867469 x 100 = -66.39%