Solution:
The problem states that the ratio of red tiles to blue tiles is 3:5 and there are 12 more blue tiles than red tiles.If we denote the number of red tiles as 3x and the number of blue tiles as 5x (where x is a common multiplier), the difference between the number of blue tiles and red tiles can be expressed as:5x - 3x = 12Solving for x:2x = 12x = 12 / 2x = 6Now, we can find the number of red tiles, which is 3 times x, or 3 * 6:3 * 6 = 18Therefore, there are 18 red tiles in the box, so the answer is A. 18.