c = ciment
n = nisip
15 c + 38 n = 3930 kg
25 c + 38 n = 4736 kg
----------------------------
10 c = 806
c = 80,6 kg
15x 80,6 + 38 n = 3930
1209 + 38 n = 3930
38 n = 3930 - 1209
38 n = 2721
n = 2721 : 38
n = 71.60
cred ca era 3936....rezolvare si cu 3936 revezi datele problemei
15 c + 38 n = 3936 kg
25 c + 38 n = 4736 kg
----------------------------
10 c = 800
c = 80 kg
15x 80 + 38 n = 3930
1200 + 38 n = 3930
38 n = 3936 - 1200
38 n = 2736
n = 2736 : 38
n = 72 kg