The total number of times Marcus rolls the two number cubes is 16 + 10 = 26.
Let's define the event E as the event that the sum of the two number cubes is even, and the event O as the event that the sum is odd.
The relative frequency of an event is defined as the number of times the event occurs divided by the total number of trials. Therefore, the relative frequency of E is:
Number of times E occurs / Total number of trials
We know that the number of times E occurs is 16, so we have:
Relative frequency of E = 16 / 26
Simplifying this fraction, we get:
Relative frequency of E = 8 / 13
Therefore, the relative frequency of the event that the sum of the two number cubes is even is 8/13.