Answer:
To make 3 gallons of punch, you need 2 cups of cranberry juice.
We can set up a proportion to find out how much cranberry juice is needed for 1 gallon of punch:
2 cups / 3 gallons = x cups / 1 gallon
To solve for x, we can cross-multiply:
2 cups * 1 gallon = 3 gallons * x cups
2 cups = 3x
x = 2/3 cup
Therefore, you would need 2/3 cup of cranberry juice to make 1 gallon of punch using this recipe.