Every time you roll two dice you can get a sum of any number between 2 and 12, inclusive.
There is 1 way to get a 2 (1 on the first and 1 on the 2nd)
There are 2 ways to get a 3 (1 on the first; 2 on the 2nd or 1 on the first; 1 on the 2nd)
There are 3 ways to get a 4 (1 on the first; 3 on the 2nd, 3 on the first; 1 on the 2nd or 2 on each)
and so on.
In total there are 36 possible combinations (think 6 sides on each die).
Of these 36 combinations, there are 6 ways to get a sum of 7:
1 and 6, 2 and 5, 3 and 4, 4 and 3, 5 and 2, 6 and 1
So the probability of rolling a 7 is 1/6 (6/36=1/6)
If you roll the pair of dice 50 times, you would expect to roll a 7,
50x(1/6) = 8.333 times
