-31.75% is the change from 315 to 215
Calculation steps:
[( 215 - 315 ) ÷ 315] x 100 = -31.75%
Formula
Percentage change = [(215 - 315) / 315] x 100
Subtract the new number by the original number
215 - 315 = -100
-100 ÷ 315 = -0.31746031746031744
-0.31746031746031744 x 100 = -31.75%