a. We know the amounts needed for 18 serving, so we can use proportions to scale this up to 108 cups. It is easy once you realize that 4 cups + 8 cups + 12 cups = 18 servings, and 18 * 6= 108, therefore you will need 6 times the amount of ingredients equally proportionated to each of the juices/seltezer. Therefore, we would need 24, 48, 72 cups of pineapple juice, orange juice, and seltzer.
b. Adding 4, 8, and 12 together, we get 24. 108 cups/24 cups of ingredients = 4.5 servings.
c. Using ratios, we see that we use 8 cups of orange juice for every 12 cups of seltzer. Dividing each side by 12, we get that we use 2/3 cups of orange juice for each cup of seltzer.
