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x = nr. de probleme rezolvate corect
y = nr. de probleme rezolvate gresit
x + y = 20 | · 2
5x - 2y = 72
------------------------
2x + 2y = 40
5x - 2y = 72
------------------------ Adunam ecuatiile
7x / = 112
x = 112 : 7 = 16 probleme rezolvate corect
y = 20 - 16 = 4 probleme rezolvate gresit