Ajar contains only one blue tile, one green tile, one red tile, and one yellow tile. if a tile is chosen at random and then replaced in the jar, and then a second tile is chosen at random, how many of the possible outcomes contain at least one red tile? (there are no answer choices)

The jar contains 1+1+1+1=4 tiles, and it's equally possible to choose any one of them in one round. Thereare 4*4=16 total possible outcomes for two rounds. First calculate the number of outcomes that don't contain a red tile. There're three possible outcomes for each round, at 3*3=9 for two rounds. Therefore, there are 16-9=7 possible outcomes that contain at least one red tile.