Question

la un concurs de cultura generala,elevi se asaza cate doi in banca,astfel incat raman 4 banci libere.daca se asaza cate unul in banca,raman 7 elevi in picioare.cate banci sunt si cati elevi participa la concurs?

Answer 1

$x \to nr. \ de \ banci \\\\ 2(x-4) \to nr. \ de \ elevi \\ x+7 \to nr. \ de \ elevi \\\\ 2(x-4)=x+7 \\\\ 2x-8=x+7 \\\\ 2x-x=7+8 \\\\ \boxed{x=15} \\\\ 15+7= \boxed{22 \ elevi}$

Answer 2

2x(X-4) =X+7
2X-8=X+7
2X-X=7+8
X=15 (numarul de banci)
15+7=22 elevi participa la concurs.