Răspuns :
1 sticla...........10 pahare..........10 invitati
x sticle ............y pahare..........20 invitati
1/x=10/20=>x=20/10=>x=2 sticle
x sticle ............y pahare..........20 invitati
1/x=10/20=>x=20/10=>x=2 sticle