The expression for the total cost of their trip is 7 + 2x + 3y.
As per the question, assuming the number of bottles to be x and number of bags to be y. The equation will have one time fee of admission, product of cost of bottles and number of bottles and product of cost of bags and number of chips bags.
The one time fee and two products will be added to form the expression. Forming the equation now -
Expression = 7 + 2x + 3y
Therefore, the expression of trip when x bottles of water were bought during the visit is 7 + 2x + 3y.
Division is the usual shortcut for repeated subtraction. You could subtract 5.5 from 264 until you get to zero. You would have to do 48 subtractions. It is easier to divide 264 by 5.5 to see how many times it goes.