287.5% is the change from 8 to 31
Calculation steps:
[( 31 - 8 ) ÷ 8] x 100 = 287.5%
Formula
Percentage change = [(31 - 8) / 8] x 100
Subtract the new number by the original number
31 - 8 = 23
23 ÷ 8 = 2.875
2.875 x 100 = 287.5%
Example