a)
[tex]\it Fie \ x,\ y,\ z\ cele\ trei\ p\breve ar\c{\it t}i.\\ \\ x+y+z=68\ \ \ \ (1)\\ \\ \{x,\ y,\ z \}\ d.\ p.\ \{4,\ 5,\ 8\} \Rightarrow \dfrac{x}{4}=\dfrac{y}{5}=\dfrac{z}{8}=\dfrac{x+y+z}{4+5+8}\ \stackrel{(1)}{\Longrightarrow}\ \dfrac{68}{17}=4 \Rightarrow\\ \\ \\ \Rightarrow\begin{cases} \it x=4\cdot4=16\\ \\ \it y=5\cdot4=20\\ \\ \it z =8\cdot4=32\end{cases}[/tex]
