Probability that a marble drawn at rondom from the bowl is not black

Number of red marbles = 6
Number of blue marbles = 4
Number of black marbles = 2
Total number of marbles = $6 + 4 + 2 = 12$

Marbles that are not black include red and blue marbles.
Number of non-black marbles = Number of red marbles + Number of blue marbles
Number of non-black marbles = $6 + 4 = 10$

Probability (not black) = $\frac{\text{Number of non-black marbles}}{\text{Total number of marbles}}$
Probability (not black) = $\frac{10}{12}$
Simplify the fraction:
Probability (not black) = $\frac{5}{6}$

The probability that a marble drawn at random from the bowl is not black is $\boxed{\frac{5}{6}}$.