Question

Mihai are o suma de bani. Daca ar cumpara 3 caiete de acelasi fel, i-ar ramane 5 lei. Daca ar cumpara 4 caiete si un penar de 2 lei, ar mai avea nevoie de inca 6 lei.
Cati lei costa un caiet?

Answer 1

$x\to cat \ costa \ un \ caiet \\\\ 3x+5 \to suma \ de \ bani \\\\ 4(x-2)+6 \to suma \ de \ bani \\\\ 4x-8+6=3x+5 \\\\ 4x-2=3x+5 \\\\ 4x-3x=5+2 \\\\ \boxed{x=7} \\\\ 3*7+5= \\\\ =21+5= \\\\ =\boxed{26 \ lei \ suma \ initiala}$