Răspuns:
2 caiete.....3 stilouri.....19 RON |×2
4 caiet.......5 stilouri.....35 RON
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4 caiete.....6 stilouri.....38 RON
4 caiet.......5 stilouri.....35 RON
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/ 1 stilou=3 RON
2c+3×3=19=>c=10:2=>c=5 RON costa un caiet