-29.9% is the change from 913 to 640
Calculation steps:
[( 640 - 913 ) ÷ 913] x 100 = -29.9%
Formula
Percentage change = [(640 - 913) / 913] x 100
Subtract the new number by the original number
640 - 913 = -273
-273 ÷ 913 = -0.29901423877327493
-0.29901423877327493 x 100 = -29.9%