Answer:
Third choice, 3/4
Explanation:
Add all the cubes together, 12 + 5 + 3 = 20
There's a 12/20, which is 3/5, chance you'll get a green cube
5/20, which is 1/4, chance you'll get a blue cube
And there's a 3/20 chance you'll get a yellow cube
The probability of not getting a blue cube is 12/20 + 3/20 = 15/20 = 3/4