The cost of an order is proportional to the number of tickets if the relation between them is constant.
Then, if we order 1 ticket the cost will be $7 + $3 = $10
And if we order 2 tickets, the cost will be $7*2 + $3 = $17
So, the relation between cost and the number of tickets is:
For 1 ticket = $10 / 1 ticket = 10
For 2 tickets = $17/ 2 tickets = 8.5
Since 10 and 8.5 are different, the cost of an order is not proportional to the number of tickets ordered.
Answer: they are not proportional