[tex]M= \{ x \in N* | x \ \textless \ 21 \} = \{ 1;2;3;4;5;6;7;8;9;10; \hdots 20 \} \\ \\
\texttt{Submultimea P} \subset \texttt{M a numerelor prime este: } \\ \\
P = \{x \in N* | x \ \textless \ 21, x = numar prim\} = \{1;2;3;5;7;11;13;17;19\} \\ \\
\texttt{M are 20 de elemente iar P are 9 elemente} \\ \\
\displaystyle \\
p = \frac{\texttt{Numar cazuri favorabile}}{\texttt{Numar cazuri posibile}} = \frac{^{5)}9}{20} = \frac{45}{100} = 45\%[/tex]
