Melissa has a bag that contains 6 red marbles, 8 yellow marbles, and 18 blue marbles. if she chooses one marble from the bag, what is the probability that the marble is not blue?

The probability that the marble she chooses  is not blue can be solve in two ways.
first way: is to solve the probability of red and yellow marbles, so that is the probability of not getting blue
P = 6 + 8 / 6 + 8 + 18P = 7/16
2nd way: is to solve the null of blue or 1 minus the probabilty of choosing blue marble
P = 1 - (18 / 6 + 8 + 18)P = 1 - ( 9 / 16)P = 7/16