I'm pretty sure your answer should be $4.50 for each drink. I multiplied the price of the popcorn (3.75 including the tax) by 4, since there are 4 people, which gave me 15. Then take 15 out of 33.00 which gave me 18. Divide 18 by 4 (number of people) and get 4.5 or 4 1/2 which equals out to $4.50 for each drink.
3.75 · 4= 15
33.00 - 15= 18
18 ÷ 4= 4.5 or 4 1/2
Hope this helps! =^-^=