-31.09% is the change from 312 to 215
Calculation steps:
[( 215 - 312 ) ÷ 312] x 100 = -31.09%
Formula
Percentage change = [(215 - 312) / 312] x 100
Subtract the new number by the original number
215 - 312 = -97
-97 ÷ 312 = -0.3108974358974359
-0.3108974358974359 x 100 = -31.09%