Primul elev :a=b+35
Al doilea elev :b
Al treilea elev:c=b+45
a+b+c=200 timbre
(b+35)+b+(b+45)=200
3b+80=200 3b=200-80 3b=120 timbre
b=120/3 b=40 timbre
Deci al doilea are 40 timbre
a=b+35 deci primul are a=40+35=75 timbre
Al treilea are c=b+45 c= 40+45 c=85 timbre
Proba a+b+c=75+40+85=200 timbre
Succes!!!