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daca a+b=7 iar b+c=10 aflati a+3b+2c

Răspuns :

daca a+b=7, iar b+c=10 atunci a+3b+2c=a+b+2b+2c=7+2(b+c)=7+20=27

a+3b+2c= (a+b)+(b+c)+(b+c)
              = 7+ 10 +10
              = 27