Question

This is a problem of probabilty. However, i can not solve it ,
please help me to solve it completely.
Thank you.

@ Wello1

Answer 1

P(2lulus) = (1/2).(1/3) + (1/2).(1/4) + (1/3).(1/4)
               = 1/6 + 1/8 + 1/12
               = (4+3+2)/12
               = 9/12

P(3lulus) = (1/2).(1/3).(1/4)
               = 1/24

P(2) + P(3) = 9/12 + 1/24
                   = 19/24