Final answer:
The domain of the function y = 3x when given the range {9,12,15} can be found by solving for x, resulting in the domain {3, 4, 5}.
Step-by-step explanation:
The domain of the function y = 3x when the range is {9,12,15} can be found by solving the equation y = 3x for x with each y value given in the range. The solution for each y value will provide the corresponding x value for the domain. For y = 9, we have x = 9/3 = 3. For y = 12, we have x = 12/3 = 4. And for y = 15, we have x = 15/3 = 5. Therefore, the domain for these range values is {3, 4, 5}.