Answer:
5/18
Step-by-step explanation:
The attached chart shows all 36 outcomes, equally likely.
There are 6 outcomes that are doubles (along a diagonal), 5 outcomes that have a sum of 8, but the (4, 4) outcome should only be counted once!
You're interested in 6 + 5 - 1 = 10 outcomes out of the 36 possible outcomes.
Probability of double or sum = 8: 10/36 = 5/18