In order to divide $306 into the ratio of 9 to 5 to 3, first you have to make each section of the ratio represented by a variable, and put it into an equation.
9x + 5x + 3x = 306
Our next step is to simplify the left side of the equation by combining all of the like terms, the ones that contain variables.
17x = 306
Finally, to solve this equation, you have to divide both sides by 17 to isolate the variable x on the left side of the equation.
x = 18
However, this is not our answer as it isn't in a ratio format and doesn't really make sense. To find our ratio, we have to multiply each of our initial numbers (9, 5, and 3) by our variable, x.
9 * 18 = 162
5 * 18 = 90
3 * 18 = 54
You can verify that these numbers are correct because if you add them together you get 306.
Your final ratio is 162:90:54.
Hope this helps! :)
If you have a separate specific question about pre-tax prices and PMed me the link, I'd be happy to help you.