Two fair cubes are rolled.
The total number of possible outcomes is 36.
These 36 possible outcomes are shown in the given figure.
We are asked to find the theoretical probability of rolling two numbers with a sum of 11.
Recall that theoretical probability is given by

The desired outcome is the sum of 11 which occurs exactly 2 times.
The total number of possible outcomes is 36.
So, the probability is

Therefore, the theoretical probability of rolling two numbers with a sum of 11 is 1/18