Răspuns :
B = { 1 /1 , 1/2 , 1/3 , 1/4 , 1/5 , 1 /6 , 1/7 , 1/8 , 1 / 9}
card B = 9
card B = 9
[tex]\displaystyle a) \\ B= \left\{ \frac{1}{1}; ~\frac{1}{2};~\frac{1}{3};~\frac{1}{4};~\frac{1}{5};~\frac{1}{6};~\frac{1}{7};~\frac{1}{8};~\frac{1}{9} \right\} \\ \\ b) \\ card \;B = \boxed{9}[/tex]