1. **State the problem:** We need to write an equation relating the total cost $C$ to the number of slices of pie $r$ eaten, given an admission fee and a per-slice cost. 2. **Identify the given information:** - Admission fee (fixed cost): 3 - Cost per slice of pie: 2 3. **Write the formula:** The total cost $C$ is the sum of the fixed admission fee plus the cost for each slice eaten: $$C = \text{admission fee} + (\text{cost per slice}) \times r$$ 4. **Substitute the values:** $$C = 3 + 2r$$ 5. **Explain:** This means you pay 3 dollars just to enter, and then 2 dollars for each slice you eat. So if you eat 0 slices, you pay 3 dollars; if you eat 1 slice, you pay 5 dollars, and so on. **Final answer:** $$C = 3 + 2r$$