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Daca 2×x+5×y=52 si 2×x+4×y=42Sa se afle y?

Răspuns :

2x+5y=52
2x+4y=42

2x+5y=52
-2x-4y=-42
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      y=10
2x+5y=52
2x+4y=42
_________
2x+5y-2x-4y=52-42
y=10