الف)

$n(s) = \left( \begin{gathered}
  9 \hfill \cr 
  6 \hfill \cr 
 \end{gathered}  \right) = \frac{{9!}}{{3! \times 6!}} = 84$

$p(A) = \frac{{\left( \begin{gathered} 
  5 \hfill \cr 
  4 \hfill \cr 
 \end{gathered}  \right)\left( \begin{gathered} 
  4 \hfill \cr 
  2 \hfill \cr 
 \end{gathered}  \right) + \left( \begin{gathered} 
  5 \hfill \cr 
  5 \hfill \cr 
 \end{gathered}  \right)\left( \begin{gathered} 
  4 \hfill \cr 
  1 \hfill \cr 
 \end{gathered}  \right)}}{{\left( \begin{gathered} 
  9 \hfill \cr 
  6 \hfill \cr 
 \end{gathered}  \right)}} = \frac{{30 + 4}}{{84}} = \frac{{34}}{{84}}$

ب)

$P(B) = \frac{{\left( \begin{gathered} 
  5 \hfill \cr 
  3 \hfill \cr 
 \end{gathered}  \right)\left( \begin{gathered} 
  4 \hfill \cr 
  3 \hfill \cr 
 \end{gathered}  \right)}}{{\left( \begin{gathered} 
  9 \hfill \cr 
  6 \hfill \cr 
 \end{gathered}  \right)}} = \frac{{10 \times 4}}{{84}} = \frac{{40}}{{84}}$