Explain: If you ever come across a question that asks you how much a number would be after 2, 3, 4, 5, and so on. All you have to do is multiply that first number with the second.
Example: if the gardener collects 20 carrots a week. How many carrots did the gardener collect in a span of 5 weeks?
Both answers are not the same. You are correct and your friend is wrong. The situation your teacher gave could have only one other interpretation that would be acceptable and that would be 8t+3 because it is the same number just in a different order.