Explicație pas cu pas:
c= sac ciment
n= sac nisip
25c.....+18n.......=1684 kg (minus )
15c......+18n.......=1284 kg
_______________________
10c..........x..........=400 kg
c=400:10 c=40 kg/ sac de ciment
25x40 + 18n=1684
1000 kg+18n=1684 kg
18n=1684-1000
18n=684
n=684:18
n=38 kg/sacul de nisip
proba
25x40+18x38=1000+684=1684 kg.
