[tex]\displaystyle \\ \\
\begin{cases}
x-y = 40 \\ \displaystyle
\frac{x}{y} =5
\end{cases} \\ \\
\begin{cases}
x-y = 40 \\
x =5y ~~~~~(substitutie)
\end{cases} \\ \\
5y- y = 40 \\
4y = 40 \\
\displaystyle \\
y = \frac{40}{4} = \boxed{10} \\
\text{Ne intoarcem la substitutie: } \\
x = 5y = 5 \cdot 10 = \boxed{50} \\ \\
Verificare: \\
x - y = 50 - 10 = 40 ~~~~~corect\\ \\
\frac{x}{y} = \frac{50}{10} = 5~~~~~corect[/tex]
