STEP 1: Find number of recipes needed for 20 servings (number of times we're multiplying original recipe) = 20 servings ÷ 8 servings per recipe = 20/8 = 2 4/8 reduce by 2 = 2 1/2 or 2.5 recipes
STEP 2: Multiply recipes needed by amount of cheese used per recipe = 2 1/2 * 12 ounces convert fraction to improper fraction = 5/2 * 12 multiply numerators = (5*12)/2 = 60/2 = 30 ounces of cheese needed
ANSWER: She needs 30 ounces of cheese to make 20 servings.