Notăm:
m - vârsta lui Mihai;
t- vârsta tatălui.
[tex]\it \left.\begin{aligned} \it m=t-24\\ \\ \it m=\dfrac{t}{3} \end{aligned}\right\} \Rightarrow t-24=\dfrac{t}{3}\Big|_{\cdot3} \Rightarrow 3t-72=t \Rightarrow 3t-t=72 \Rightarrow 2t=72 \Rightarrow \\ \\ \\ \Rightarrow t=72:2 \Rightarrow t=36\ ani\ \ \ \ \ (*)\\ \\ m=\dfrac{t}{3} \stackrel{(*)}{\Longrightarrow}\ m=\dfrac{36}{3} \Rightarrow m=12\ ani[/tex]