Răspuns: 21 banci si 35 elevi
Explicație pas cu pas:
Notez numarul bancilor cu ,,b"
Datele:
2 × ( b - 3 - 1 ) + 1 → cate 2 elevi in banca, ar ramane 3 banci libere si un elev ar sta singur in banca
3 × ( b - 9 - 1 ) + 2 → cate 3 elei in banca, raman 9 banci libere si 2 elei intr-o banca
_____________________________________________________
3 × ( b - 10 ) + 2 = 2 × ( b - 4 ) + 1 => elevi
3 × b - 30 + 2 = 2 × b - 8 + 1
3 × b - 28 = 2 × b - 7
3 × b - 2 × b = - 7 + 28
b = 21 ( banci )
2 × ( 21 - 3 - 1 ) + 1 = 2 × 17 + 1 = 35 elevi
sau:
3 × ( 21 - 9 - 1 ) + 2 = 3 × 11 + 2 = 35 elevi
