Answer:
28 non-blue marbles.
Step-by-step explanation:
Initial probability of choosing a blue marble = 4/12
Let the number of non-blue marbles to be added be x.

(cross multiply)

Let's have this equation equal y first. All we have to do is add y to both sides and subtract 4 from both sides.
5x-4=y
Now, to get a parallel line, the y intercept has to change. The y intercept (the -4 in the equation) can be an infinite amount of number but -4.
Let's choose 6. We would have 5x+6=y or you could put it in the way the other equation was, 5x-y=-6.
The digit 9 in 39 is the ones place.