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Se stie ca:a+2b+c=51si2a+b+2c=42. Aflati a+ b + c

Răspuns :

[tex]a+2b+c=51\\2a+b+2c=42\\(a+2b+c)+(2a+b+2c)=51+42\\3a+3b+3c=93\\Dam.factor.comun.pe.3:\\3*(a+b+c)=93\\a+b+c=\frac{93}{3}\\a+b+c=31\\Sfarsit![/tex]