To find the probability of the sum of the numbers on two cubes (dice) equaling 8, we first need to determine the total number of possible outcomes and then how many of those outcomes result in a sum of 8.
Each number cube has 6 faces, so when rolling two cubes, the total number of possible outcomes is:
\[ 6 \times 6 = 36 \]
Next, we will find the combinations of the two cubes that add up to 8. Here are the possible pairs:
- (2, 6)
- (3, 5)
- (4, 4)
- (5, 3)
- (6, 2)
We see that there are 5 pairs that result in a sum of 8.
Now we can calculate the probability:
\[ \text{Probability} = \frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}} = \frac{5}{36} \]
Thus, the probability that the sum of the two number cubes equals 8 is
\[ \boxed{\frac{5}{36}} \]