Răspuns: 15 banci si 33 elevi
Explicație pas cu pas:
2 × b + 3 → cate 2 elevi in banca, raman 3 elevi in picioare
3 × ( b - 4 ) → cate 3 elevi in banca, raman 4 banci libere
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3 × ( b - 4 ) = 2 × b + 3 ⇒ elevi
3 × b - 12 = 2 × b + 3
3 × b - 2 × b = 3 + 12
b = 15 banci
2 × 15 + 3 = 33 elevi
Verific:
3 × ( 15 - 4 ) = 3 × 11 = 33 elevi