-17.63% is the change from 777 to 640
Calculation steps:
[( 640 - 777 ) ÷ 777] x 100 = -17.63%
Formula
Percentage change = [(640 - 777) / 777] x 100
Subtract the new number by the original number
640 - 777 = -137
-137 ÷ 777 = -0.17631917631917632
-0.17631917631917632 x 100 = -17.63%