a+b+c=340
a+b=80+b+c
b=50+c
80+b+c+b+c=340
80+2b+2c=340
2b+2c=340-80=260 2(b+c)=260 b+c=130,inseamna ca a+b=80+130=210.acum inlocuim:210+c=3400 rezulta ca c=130.atunci b=50+130=180.stim ca
t este c si b aflam pe a. a+180+130=340.a=30.facem proba:130+210+30=340