Final answer:
To scale the recipe, Victor and Clara need to multiply all amounts of the ingredients by a factor of 2.
Step-by-step explanation:
To scale the recipe, Victor and Clara need to multiply all amounts of the ingredients by 6/3. This means they need to increase the quantities of the ingredients by a factor of 2. When scaling a recipe, you multiply all the amounts of the ingredients by the scaling factor to ensure the proportions remain the same. In this case, the factor used to scale the recipe is 2.