probability (easy stuff i know but i just don't remember how to do it)
a bag contains 4 red marbles, 5 blue marbles, 1 black marble and 3 yellow marbles. if a marble is drawn at random, find the prob. of not drawing a red marble
You have 4 red marbles and 13 marbles in total. Thus, your chance of drawing a red marble is 4/13 and your chance of NOT drawing a red marble is 9/13.
-Andy