Final answer:
The expression 25 + 9n represents the total cost of t-shirts for the science club, where n is the number of shirts.
Step-by-step explanation:
The total cost of t-shirts for the team can be calculated using the expression: 25 + 9n, where n is the number of t-shirts. The $25 represents the one-time set-up fee, and $9 represents the cost of each shirt. By multiplying the number of shirts with the cost per shirt and adding the set-up fee, we can determine the total cost.