Final answer:
The ratio of blue balls to white balls is 12:9, which can be simplified to 4:3.
Step-by-step explanation:
The question asks for the ratio of blue balls to white balls in a box containing a total of 15 black balls, 12 blue balls, and 9 white balls. To find this ratio, we only need to consider the number of blue balls and the number of white balls.
The ratio of blue balls to white balls is found by dividing the number of blue balls by the number of white balls. In this case, there are 12 blue balls and 9 white balls, which gives us a ratio of:
12 blue balls : 9 white balls
This can also be simplified by dividing both numbers by their greatest common divisor, which is 3. So, the simplified ratio is:
4 blue balls : 3 white balls