410,860+m*20=489.000 g
410.860 +m*20=489.000
m*20 = 489.000-410.860
m*20= 78.140
m= 78.140:20 = 3.907
m * 20= 78.140
m = 78.140 / 20 = 3.907
Ответ:3.907