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Calculati 2a+5b+3c , stiind ca a+b=20 si b+c=30 .

Răspuns :

2a+5b+3c

a+b=20
b+c=30

2a+2b+3b+3c
2(a+b)+3(b+c).   inlocium
2*20+3*30=
40+90=130