The table shows the cost of tickets at a carnival.

number of tickets total cost
1 $2.50
2 ?
3 $7.50
4 ?
5 $12.50
6 $15.00
7 $17.50

assuming that the cost of tickets follows the same pattern as the number of tickets increases, find the values that are missing from the table and determine the total cost of nine tickets.

the cost of two tickets , the cost of four tickets , and the cost of nine tickets is

We can use the equation (y2-y1)/(x2-x1) to find the slope which represents the ticket price
We can use any two points given so we'll use the points (5, 12.5) and (6, 15.00)

We can then plug the points into the formula (15-12.5)/(6-5)
2.5/1 =2.5
So a single ticket costs 2.5

Meaning if someone buys two tickets, it would be 2.5×2=5
The cost of two tickets is $5

If they buy four tickets, we would do 4×2.5=10
The cost of four tickets is $10

If someone were to buy nine tickets, we would do 2.5×9=22.5
The price of nine tickets is $22.5