Answer:
B
Step-by-step explanation:
You have 3 red marbles and say x non-red marbles. Then you get the following equation:
[tex]\frac{3}{3+x} = \frac{1}{5}[/tex]
We can solve this equation by doing cross multiplication:
[tex]3*5 = 3 + x[/tex]
And solve for x to be 12.
