Răspuns :

AlecSanDaRuid
E=3a+6b+2b+6c=3(a+3b)+2(b+3c)=3*5.2+2*4.2=15.6+8.4=24
Ilovechocolateid
a+2*b=5.2 inmultim relatia cu 3 si rezulta 3*a+3*2*b=5.2*3 rezulta 3*a+6*b=15,6 relatia (1)
b+3*c=4.2 inmultim relatia cu 2 si rezulta 2*b+2*3*c=4.2*2 rezulta 2*b+6*c=8.4 relatia (2) 
Si aduni relatia (1) cu relatia (2): 3*a+6*b+2*b+6*c=15.6+8.4 rezlta 3*a+8*b+6*c=24
Deci E=24

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