What is the probability that the sum of the numbers showing on the cubes is at least 9 when you role two cubes?

P(x≥9) = 0.27777... ≈ 28%

Let x equal to the sum of the numbers showing on dice when you roll a pair of dice.

P(x=12) = 1/36; P(x=11) = 2/36; P(x=10) = 3/36; P(x=9) = 4/36.

So, P(x≥9) = P(x=12) + P(x=11) + P(x=10) + P(x=9) = 1/36 [1+2+3+4] = 10/36

P(x≥9) = 0.2777... ≈ 28%