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Daca a+b=7,iar b+c=10,aflati a+3b+2c.

Răspuns :

a+b=7
2b+2c=20
-----------------------Adunand relatiile:
a+3b+2c=27


{a+b=7

{b+c=10       /*2


{a+b=7

{2b+2c=20           (+)

a+3b+2c=27