Use tables or tree diagrams to list situations:

1 is 4, 5, 6, 7 and 5, 6, 7, 8 respectively.

They are 2 4, 5, 6, 7 and 6 7 8 9 respectively.

3 4, 5, 6, 7 and respectively: 7, 8, 9, 10.

It can be seen that the total number is 12, of which 6 are even and 6 are odd.

So the probability that the sum is even and odd is 0.5, so the game is fair.