Răspuns: 20 banci si 45 elevi
Explicație pas cu pas:
Notez cu ,,b" = numarul total de banci
Datele problemei:
3 × ( b - 5 ) → elevi ( cate 3 elevi in banca, raman 5 banci libere)
2 × b + 5 → elevi ( cate 2 elevi in banca, raman 5 elevi in picioare)
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3 × ( b - 5 ) = 2 × b + 5 -> elevi
3 × b - 15 = 2 × b + 5
3 × b - 2 × b = 5 + 15
b = 20 ( banci )
20 × 2 + 5 = 40 + 5 = 45 elevi
sau:
3 × ( 20 - 5 ) = 3 × 15 = 45 elevi