Is it possible to prepare a lunch that contains three servings of Food A and three servings of Food B and still satisfy the constraints on cost , amount of sugar , and amount of protein ? Explain

No, because right away if you multiply each number by 3 for Food A, there would already be 39 grams of protein, and 12 grams of sugar. Then in Food B there would be 27 more grams of protein, and there would be 18 grams of sugar. Therefore making a total of $4.80. 30 grams of sugar and 66 grams of protein.