A bag contains 12 marbles: 5 are orange, 3 are blue, and the rest are red. If one marble is selected at random from the bag, what is the probability that it will be red or blue?

7/12

Step-by-step explanation:

The probability is the number of events out of the number of outcomes. The total number of outcomes is the number of marbles which is 12. The number of events is the number of red or blue marbles which is 3 + 4 = 7. This is true since there are 3 blue listed and since 12 - 5 - 3 = 4 red.

The probability is a ratio or fraction and should be written as 7 / 12.