a numarul de elevi
b numarul de banci
1 elev in banca: a=b+6
2 elevi in banca:
-banci complet libere: 4
-banci partial ocupate: 1
-banci complet ocupate: b-4-1=b-5
-numar elevi: a=2×(b-5)+1
Avem 2 ecuatii:
a=b+6
a=2(b-5)+1
b+6=2b-10+1
b+6=2b-9
Deci b=15 banci
a=b+6=21 elevi