Answer:
10 tickets
Explanation:
There is always a fixed cost of 8.75 whenever you want to avail the service.
So 8.75 is fixed
Now, each ticket, t, costs 18.50, so it would cost Sandra 18.5*t to buy t tickets. Of course, this has to be LESS THAN or EQUAL TO 200. We can now write and inequality of this form shown below (remember 8.75 is fixed):

Let's solve this and find the max number of tickets Sandra can buy:

You can't buy fractional amount, so Sandra can basically buy 10 tickets