[tex]\displaystyle\\
\text{ Folosim formulele:}\\
\text{1) Treimea lui a }=\frac{1}{3}\times a\\\\
\text{2) Intreitul lui a }=3\times a\\\\
\text{Rezolvare:}\\\\
\text{Notam numarul cu } n.\\\\
\text{Treimea lui }n=\frac{1}{3}\times n\\\\
\text{Treimea treimii lui n este egal cu 5 }\\\\
\frac{1}{3}\times \Big(\frac{1}{3}\times n\Big)=5\\\\
\frac{1}{3}\times \frac{1}{3}\times n=5\\\\
\frac{n}{9}=5\\\\
n = 5\times9=\boxed{45}\\\\
\text{Intreitul lu n este:}\\\\
3n=3\times 45 = \Boxed{135}
[/tex]
