[tex]\overline{ab}=5*a+3*b \\\\ 10a+b=5a+3b \\\\ 10a-5a=3b-b \\\\ 5a=2b \ \ \ (1)\\\\ \Longrightarrow \left \{ {{5|b} \atop {2|a}} \right. \Longrightarrow \left \{ {{b \ \in \ M_5} \atop {a \ \in \ M_2}} \right. \\\\ a;b-cifre\ \ \ ; \ \ \ a \neq 0 \ \ \ (2)\\\\\ \longrightarrow \left \{ {{b \in \{0;5} \} \atop {a \in \{2;4;6;8\}}} \right. \ \ \ (3) \\\\\\ Din \ (1),(2) \ si \ (3) \ \Longrightarrow \boxed{b=5} \\\\\\ a= \frac{2b}{5}= \frac{2* \not 5}{\not 5} \to \boxed{a=2} [/tex]
[tex]\boxed{\boxed{\overline{ab}=25}}[/tex]
