fie 'Ion" numarul;de probleme rezolvatede Ion si "Stefan', numarulde probl.rezolvatede Stefan
atunci
unitate timp =Ion/4=Stefan/5=(proportiiderivate)=(Ion+Stefan)/(4+5)=(Ion+Stefan)/9=72/9=8
Ion/4=8⇒Ion=32
Stefan/5=8⇒Stefan=40
verifuicare
32/4=40/5
32+40=72
adevarate ambele, bine rezolvat