Answer:
The expression that represents the estimated cost for the party is T=s×i
Explanation:
1) We can get an estimated cost for the party by using the following expression:
T=s×i
where:
T: total cost of the ice cream party ($)
s: number of ninth students (person)
i: unit cost of ice cream ($/person)
2) If we choose the letter "s", it can take whole number values.
For example: s={1,2,3,4,5,...,25}
If we choose the letter "i", it can take rational values (sometimes the price of the items are not expresed as a whole number).
For example: s={1.25,2.50,3.00,4.75,5.00}