Final answer:
Chef Selena can make a maximum of 39 servings of her dish.
Step-by-step explanation:
To find out how many servings of Chef Selena's dish she can make, we need to divide the total amount of each ingredient by the amount required per serving. The amount of pasta divided by 12 pounds gives us the number of servings of pasta, the amount of sauce divided by 6 pounds gives us the number of servings of sauce, and the amount of onions divided by 12 pounds gives us the number of servings of onions. We take the smallest number to find the maximum number of servings, as we can only make as many servings as the ingredient with the least amount.
So, Chef Selena can make a maximum of 478/12 = 39 servings of her dish.