3t cartofi..........5t mere..........2600 lei /x4
4t cartofi..........1t mere..........1200 lei /x3
12t cartofi+20t mere=10400 lei
12t cartofi+ 3t mere= 3600 lei
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// 17 t mere= 6800 lei
1 tona mere= 6800:17
1 tona mere=400 lei
1 tona=1000kg
1000kg=400 lei
1kg= x lei
x=400/1000
x= 0,4 lei costa 1 kg de mere