Răspuns :
b+f=24------f+6+f=24-----2f=24-6------2f=18---------f=18:2--------f=9
b=f+6------------b=9+6=15
verificare: 15+9=24 elevi
b+f=24------f+6+f=24-----2f=24-6------2f=18---------f=18:2--------f=9
b=f+6------------b=9+6=15
verificare: 15+9=24 elevi