Not sure what marble you want the probability of finding so I just did them all. Your probability of drawing a marble of any kind is 15/15 or 1, because every single ball in the bag is a marble.
Your chances of drawing a spotted marble are 5/15 or 1/3.
Your chances of drawing a checkered marble or a striped marble are 4/15
Your chances of drawing a bricked marble are 2/15