a=2*b +7
b=3*c+3 => c=(b-3)/3
inlocuim cele doua in prima ecuatie obtinem:
2*b+7 +b+ (b-3)/3 = 56 (inmultim cu 3 atat in dreapta cat si in stanga, pt a scapa de fractie ) =>
=>6*b+21+3b +b-3=168 =>
10*b +18 =168 => 10*b =150 => b=15
cum a =2*b+7 => a=30+7=37
iar c=(b-3)/3 =(15-3)/3 =12/3 =4
facand proba: a+b+c =37+15+4 =56 (adevarat )
