#### Answer

If the least expensive snack is bought, you can afford at most 15 snacks.

#### Work Step by Step

Step 1) If the most expensive sandwiches and drinks are ordered, the cost is: 3(7) + 3(2) = 27
Step 2) If the least expensive sandwiches and drinks are ordered, the cost is: 3(4) + 3(1) = 15
Step 3) If the total bill is $15 (least expensive sandwiches), we would still have 15 left, so we could buy 15 more snacks.