Add up to get the total number of marbles: (8 + 6 + 12 + 10) = 36
Then subtract the number of blue marbles from the total amount of marbles: 36 - 8 = 28.
28 signifies the amount of marbles that are NOT blue.
So the probability is: 28/36 = 0.77 = About 77%
The final answer is 7/9.