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Dorneanucristin
a fost răspuns

Calculati suma a+5b+7c,stiind ca 3a+9b=51 si 4b+14c=62

Răspuns :

Primăvară2017
a+5b+7c=?

3a+9b=51
3×(a+3b)=51
a+3b=51:3
a+3b=17
a=17-3b

4b+14c=62
2×(2b+7c)=62
2b+7c=62:2
2b+7c=31
7c=31-2b

a+5b+7c=17-3b+5b+31-2b=48