2t cartofi..........3t ceapa.........8100 lei
2t cartofi..........7t ceapa.........14900 lei
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// 4t ceapa.........6800 lei
1t ceapa= 6800:4
1t ceapa= 1700 lei
2t cartofi+3x1700=8100
2t cartofi+5100=8100
2t cartofi=3000
1t cartofi= 1500 lei
2x1500+3x1700=3000+5100=8100 lei