When you have equal probabilities, the probability of a Happy Event is ways-to-be-Happy/total-possibilities. John has a bucket with 300 glass marbles in it. 100 of the marbles have 'spots,' the rest of the marbles are one of the solid colors blue or green or black or white. If John draws one marble at random out of his bucket, each of the individual marbles is equally likely to be chosen. What is the probability he gets a 'spots' marble?