11
15+12v=69
5c+7v=29=> 5c=29-7v
si inlocuim in prima relatie
3(29-7v) + 12v=69
87-21v+12v=69
-9v=-18
v=2lei
5c=29-7v
5c=29-7*2
5c=29-14
5c=15
c=3lei
asadar un kg de cartofi costa 3 lei si un kg e varza costa 2 lei
12. 3c+5p=2300=> 3c=2300-5p =>c=(2300-5p)/3
4c+2p=1200
4* (2300-5p)/3 +2p=1200
4(2300-5p) +6p=3600
9200-20p+6p=3600
-14p=-5600
p=400
c=(2300-5*400)/3
c=(2300-2000)/3
c=300/3
c=100
asadar 1c+1p=100+400=500g
