I still have this question that if we say that 1,2 or 5 has occured then the sample space
contains (1,1),(1,2),(1,3),(1,4),(1,5),(1,6),(2,1),(2,2),(2,3),(2,4),(2,5),(2,6),,(5,1),(5,2),(5,3),(5,4),(5,5),(5,6).
And we need to choose :
(1,5),(1,6),(2,4),(2,5),(2,6),(3,3),(3,4),(3,5),(3,6)
So the probability=9/18=1/2.
And then the answer should be 1/6+1/2=2/3.
I know its a silly question but what is wrong with my logic??