1. **State the problem:** Luis needs to find the equation for the total cost $y$ to pour a concrete slab with area $x$ square feet, given an initial cost of 75 and an additional 2.50 per square foot. 2. **Formula and explanation:** The total cost $y$ is the sum of the fixed initial cost and the variable cost depending on the area. This can be expressed as: $$y = \text{initial cost} + (\text{cost per square foot}) \times x$$ 3. **Substitute values:** $$y = 75 + 2.5x$$ 4. **Rewrite in standard form:** $$y = 2.5x + 75$$ 5. **Interpretation:** This means for every square foot, the cost increases by 2.5, plus a fixed 75. 6. **Answer:** The correct equation is option A: $y = 2.5x + 75$.