Răspuns:
b+3=a=>b=a-3
a+(a-3)+3a=72
a+a-3+3a=72
5a=72+3
5a=75
a=15
b=12
c=45
a+b+c=72
a=b+3
c=3•a=>c=3(b+3)=>c=3b+9
b+3+b+3b+9=72
5b=72-12=>b=60:5=>b=12
a=12+3=>a=15
c=3·15=>c=45
verificare: 15+12+45=72
