1. **State the problem:** We need to find how many different posters can be made using one poster board and one marker. 2. **Identify the given information:** There are 3 different colors of poster board and 4 different colors of markers. 3. **Formula used:** The total number of different posters is the product of the number of choices for poster boards and markers because each poster board can be paired with each marker. $$\text{Total posters} = \text{Number of poster boards} \times \text{Number of markers}$$ 4. **Calculate:** $$3 \times 4 = 12$$ 5. **Conclusion:** There are 12 different posters that can be made by using one poster board and one marker.