IF we throw 2 dice then there are 6 possible outcomes of having same number on both dice, namely
(1,1),(2,2),(3,3),(4,4),(5,5),(6,6)
And total 36 possible outcome of throwing two dice.
Therefore probability of getting same numbers on both dice =6/36
Hence probability of not getting same numbers on both dice will be
1-probability( Getting same number on both dice)
=1-6/36
=30/36
=5/6