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stiind ca 2a+b+3c=123 , iar 2a+3b+c=77 calculati a+b+c

Răspuns :

2a+b+3c=123
2a+3b+c=77   adunam cele trei relatii si rezulta
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4a+4b+4c=200 /:4  acum impartim relatia la 4 => a+b+c=50
[tex]2a+b+3c=123 \\ ------->(+) --> 4a+4b+4c=200|:4 =>a+b+c=50\\ 2a+3b+c=77 [/tex]