notam multimea {0,1,2,....20} cu A => A={0,1,2,....20}
card A = 21
M4 = {0,4,8,12,16,20...}
[tex]P= \frac{numarul~de~cazuri~favorabile}{numarul~de~cazuri~posibile} [/tex]
[tex] P=\frac{6}{21} [/tex] care se simplifica prin 3 si rezulta [tex]P=\frac{2}{7} [/tex]