Answer :
[tex]\displaystyle |\Omega|=\binom{40}{2}=\dfrac{40!}{2!38!}=\dfrac{39\cdot40}{2}=780\\|A|=\binom{10}{2}=\dfrac{10!}{2!8!}=\dfrac{9\cdot10}{2}=45\\\\P(A)=\dfrac{45}{780}=\dfrac{3}{52}\approx5,8\%[/tex]
[tex]\displaystyle |\Omega|=\binom{40}{2}=\dfrac{40!}{2!38!}=\dfrac{39\cdot40}{2}=780\\|A|=\binom{10}{2}=\dfrac{10!}{2!8!}=\dfrac{9\cdot10}{2}=45\\\\P(A)=\dfrac{45}{780}=\dfrac{3}{52}\approx5,8\%[/tex]