grâu + porumb + orz =55 tone
grâu + porumb = 42 tone
porumb + orz = 40 tone
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tone din fiecare fel = ?
orz = 55 - 42
orz = 13 tone
grâu = 55 - 40
grâu = 15 tone
porumb = 40 - 13
porumb = 27 tone